Association between patella alta and the prevalence and worsening of structural features of patellofemoral joint osteoarthritis: the multicenter osteoarthritis study

Does sex and region affect the patella position? A multi-center study of 2000 cases

PURPOSE

As patella height can affect the outcome of total knee arthroplasty (TKA) in a number of ways, this study aimed to investigate whether factors such as region, sex and age play a role in causing differences in patella height.

METHODS

Between the 1st of March and the 31st of December 2022, 2000 patients from 7 different countries (Turkey, Saudi Arabia, Germany, Austria, Italy, Spain, and the United Kingdom) awaiting elective TKA were enrolled in this study. Lateral radiographs of the knee with the femoral condyles fully overlapped were used to measure the Insall-Salvati index. The patella height measurements were then correlated with age, sex and region to see if there were any patterns of distribution.

RESULTS

From ten different hospitals across seven countries, 2,000 patients were collected. Approximately, 50% of the groups were female and 50% were male with a median age at surgery of 59 years (± 20 years). There were no significant differences in patella position based on age, region or sex between the different study populations, although there were significant differences between patients from different countries.

CONCLUSION

Patella height showed significant variability within our patient cohort, even between different populations within the same country of origin. However, it should be noted that age, sex and country of origin do not appear to influence patella height in the preoperative planning of knee surgery.

The association between patella alignment and morphology and knee osteoarthritis

OBJECTIVE

This study aims to quantitatively assess the relationship between the patella alignment and morphology and knee osteoarthritis (KOA), as well as the kinematics and kinetics of the knee, using gait analysis.

METHODS

Eighty age-matched patients with KOA and control subjects were evaluated. Incident radiographic osteoarthritis (iROA) was identified using a Kellgren-Lawrence (KL) grade of ≥ 2. The modified Insall-Salvati ratio (Mod-ISR), patellar tilt angle (PTA), and patella index (PI) were utilized to evaluate the sagittal and transverse alignment of the patella and its morphology, respectively. Regression analyses were conducted to explore associations between patellar measurements and KOA, iROA, kinematics, and kinetics.

RESULTS

Significant differences were observed between the control and KOA groups in terms of KL grade, patella alta, abduction angle, and reaction force to the ground (P < 0.05, respectively). Following adjustment for covariates, a significant positive association was found between patella alta and KOA (OR = 0.307, 95%CI: 0.103 to 0.918, P = 0.035). Additionally, a significant negative association was observed between PTA and abduction angle (B = -0.376, 95%CI: -0.751 to -0.002; P = 0.049). The PI exhibited a statistically significant association with log-transformed vertical ground reaction force (B = 0.002, 95%CI: 0.001 to 0.003, P = 0.002). Furthermore, adjustment for covariates did not reveal any significant correlations with other indicators (P > 0.05, respectively).

CONCLUSION

This study provides further evidence that proper alignment and morphology of the patella might be associated with maintaining normal biomechanical function. In addition, intervention measures targeting relevant patellar parameters, such as Mod-ISR, PTA, and PI, may positively impact KOA treatment outcomes.

Clinical reasoning of ultrasound imaging-guided manual passive manipulation for adhesion prevention in a patient with total knee arthroplasty: a case report

INTRODUCTION

Patients with total knee arthroplasty occasionally develop postoperative abnormalities such as posttraumatic knee stiffness and arthrofibrosis, which may affect activities of daily living. However, there are no clear assessment methods or interventions for knee stiffness. Musculoskeletal ultrasound imaging enables real-time evaluation of mobility and flexibility of tissues. The purpose of this case report was to describe the use of musculoskeletal ultrasound imaging for evaluating the optimal location and methods of passive manipulation.

CASE DESCRIPTION

The patient was an 82-year-old woman who had undergone total knee arthroplasty. She was unable to climb stairs due to limited knee flexion. Based on the results of musculoskeletal ultrasound imaging assessment, we hypothesized that the knee flexion limitation was caused by decreased sliding movement of the suprapatellar pouch. Hence, we performed passive manipulation on the tissue with decreased sliding under musculoskeletal ultrasound guidance.

OUTCOMES

The patient's knee flexion angle increased from 90° to 110° within 1 week of intervention, and her gait speed improved from 16.48 to 13.2 s per 10 m. Furthermore, after the intervention, she was able to climb 10 steps using a handrail.

DISCUSSION

Ultrasound imaging is important because it allows the examination of tissues with mobility changes such as in arthrofibrosis. Our work highlights the use of musculoskeletal ultrasound imaging for identifying the target region for therapy and for providing guidance during passive manipulation.

Comparative Study of the Pain, Function, and Biomarkers of Joint Disease in the Transition to Adulthood in Individuals With and Without Cerebral Palsy

BACKGROUND

Biomarkers have potential to identify early signs of joint disease. This study compared joint pain and function in adolescents and young adults with cerebral palsy compared with individuals without.

METHODS

This cross-sectional study compared individuals with cerebral palsy ( n = 20), aged 13-30 yrs with Gross Motor Function Classification System I-III and age-matched individuals without cerebral palsy ( n = 20). Knee and hip joint pain measured using Numeric Pain Rating Scale and Knee injury and Osteoarthritis Outcome Score and Hip dysfunction and Osteoarthritis Outcome Score surveys. Objective strength and function were also measured. Biomarkers for tissue turnover (serum cartilage oligomeric matrix protein, urinary C-terminal crosslinked telopeptide of type II collagen) and cartilage degradation (serum matrix metalloproteinase 1, matrix metalloproteinase 3) were measured in blood and urinary samples.

FINDINGS

Individuals with cerebral palsy had increased knee and hip joint pain, reduced leg strength, reduced walking and standing speeds, and ability to carry out activities of daily living ( P < 0.005) compared with controls. They also had higher serum matrix metalloproteinase 1 ( P < 0.001) and urinary C-terminal crosslinked telopeptide of type II collagen levels ( P < 0.05). Individuals with cerebral palsy who were Gross Motor Function Classification System I and II demonstrated reduced hip joint pain ( P = 0.02) and higher matrix metalloproteinase 1 levels ( P = 0.02) compared with Gross Motor Function Classification System III.

INTERPRETATION

Individuals with cerebral palsy with less severe mobility deficits had higher matrix metalloproteinase 1 levels likely due to more prolonged exposure to abnormal joint loading forces but experienced less joint pain.

Influence of medial patellofemoral ligament reconstruction on patellar tracking and patellofemoral contact pressures in patella alta

Knee squatting was simulated to characterize the influence of medial patellofemoral ligament (MPFL) reconstruction on patellar tracking and contact pressures for knees with mild patella alta (Caton-Deschamps index = 1.3-1.4). Eight computational models represented knees in the pre-operative condition and following MPFL reconstruction. MPFL reconstruction significantly reduced patellar lateral tracking at low flexion angles based on bisect offset index, significantly decreased the maximum lateral pressure in mid-flexion, and significantly increased the maximum medial pressure in mid-flexion. MPFL reconstruction improves patellar stability for knees with mild patella alta and can reduce the pressure applied to lateral cartilage on the patella.

Strength and passive stiffness of the quadriceps are associated with patellar alignment in older adults with knee pain

BACKGROUND

Maintaining normal patellar alignment is important for knee health. Altered activation of individual quadriceps muscles have been found related to patellar alignment. However, the relationships between strength and passive stiffness of the quadriceps and patellar alignment remains unexplored.

METHODS

Participants aged between 60 and 80 years with activity-induced knee pain were recruited. Knee pain was quantified using an 11-point numeric rating scale. Quadriceps strength was assessed using a Cybex dynamometer and passive stiffness of rectus femoris, vastus lateralis, and vastus medialis were measured by shear-wave ultrasound elastography. Patellar alignments were assessed using MR imaging. Linear regression was used to examine relationships between quadriceps properties and patellar alignments with and without controlling for potential covariates.

FINDINGS

Ninety-two eligible participants were assessed (71.7% females, age: 65.6 ± 3.8 years; pain scale: 4.6 ± 2.0), most of whom had knee pain during stair climbing (85.9%). We found that 17% of patellar lateral tilt angle could be explained by lower quadriceps strength (adjusted R2 = 0.117; P < 0.001), especially in females (R2 = 0.281; P < 0.001; adjusted R2 = 0.211; P < 0.001). In addition, a higher stiffness ratio of vastus lateralis/medialis accounted for 12% of patellar lateral displacement (adjusted R2 = 0.112; P = 0.008).

INTERPRETATION

Quadriceps strength and relative stiffness of lateral to medial heads are associated with patellar alignment in older adults with knee pain. It suggests that quadriceps weakness and relatively stiffer lateral quadriceps may be risk factors related to patellar malalignments in the elderly.

Effect of Patellofemoral Arthroplasty on Patellar Height in Patients with Patellofemoral Osteoarthritis

Osteoarthritis (OA) in the knee is common, painful, and may be uni- or multicompartmental. The compartment affected by arthritis may be due to trauma, malalignment (varus or valgus), or in the case of patellofemoral OA, patella alta. Patellofemoral arthroplasty (PFA) is an effective partial knee replacement surgery for patellofemoral OA. We hypothesized that PFA can decrease patellar height. In addition, we predicted better outcomes for patients with patella alta before PFA and those whose patellar heights decreased after PFA. This is a retrospective cohort study of PFA patients from 2012 to 2020. Before and after PFA, we measured patellar heights on X-ray images and collected patient-reported outcome measures (PROMs) (International Knee Documentation Committee score, Kujala Anterior Knee Pain Score, and Veterans RAND 12-Item Health Survey for mental and physical health). Statistical analyses assessed PROMs and compared outcomes based on pre- and postoperative patella height. Of 133 knees, 73% presented with patella alta and 61% had patellar heights that decreased after PFA. Compared with patients who did not present with patella alta, patients with patella alta reported similar outcomes with respect to knee function, pain, and general physical and mental health. Compared with patients whose patellar heights decreased after PFA, patients whose knees did not decrease in height reported greater improvements in pain and function. Our findings suggest that patella alta is commonly found in patients with patellofemoral OA and that PFA can decrease patellar height. Future studies are needed to assess whether patellofemoral OA patients with greater degrees of patella alta would benefit from staged or concurrent tibial tubercle distalization.

Differences in the Severity and Location of Patellofemoral Cartilage Damage Between Instability Patients With and Without Patella Alta

Background

Patella alta is a risk factor for recurrent patellar instability. Differences in chondral injury in patients with patellar instability between patella alta and patella norma have not been evaluated.

Purpose

To analyze whether preoperative cartilage damage differs in severity and location between patellar instability patients with and without patella alta.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients with patellar instability who underwent patellar realignment surgery at a single institution with preoperative magnetic resonance imaging (MRI) scans were included. After measurement of Caton-Deschamps index (CDI) on MRI, patients were divided into patella alta (CDI ≥1.3) and patella norma groups. The area measurement and depth and underlying structures (AMADEUS) score was used to quantify cartilage defect severity on MRI.

Results

A total of 121 patients were divided into patella alta (n = 50) and patella norma (n = 71) groups. The groups did not differ significantly in sex ratio, age at MRI, body mass index, mean reported number of previous dislocations, or mean interval between first reported dislocation and date of MRI. A total of 34 (68%) of the patella alta group and 44 (62%) of the patella norma group had chondral defects (P = .625) with no significant between-group differences in defect size (P = .419). In both groups, chondral injuries most affected the medial patellar facet (55% in patella alta vs 52% in patella norma), followed by the lateral facet (25% vs 18%), and lateral femoral condyle (10% vs 14%). A smaller proportion of patients had full-thickness defects in the patella alta compared with the patella norma group (60% vs 82%; P = .030). The overall AMADEUS score was higher for the patella alta versus the patella norma group (68.9 vs 62.1; P = .023), indicating superior articular cartilage status.

Conclusion

Patients with patella alta had less severe cartilage injury after patellar instability, including a lower proportion with full-thickness defects and better overall cartilage grade. The location of injury when present was similar between alta and norma, with most defects affecting the medial facet, lateral facet, and lateral femoral condyle in descending frequency.

Patella height influences patellofemoral contact and kinematics following cruciate-retaining total knee replacement

The role of patella height is discussed controversially in total knee arthroplasty (TKA). Therefore, this computational study aims to systematically analyze the biomechanical effect of different patella heights on patellofemoral (PF) forces and kinematics after cruciate-retaining (CR) TKA. We implemented a CR bicondylar TKA with a dome patellar button in a validated dynamic musculoskeletal multibody model of a male human knee joint. Retropatellar dynamics (contact force [N], shear force [N], patellar shift [mm], tilt [°], and rotation [°]) were evaluated during dual-limb squat motion (flexion from 0° to 90°) with simulated active muscle forces and the effects of different patella heights (Blackburne-Peel [BP] ratio of 0.39, 0.49, 0.65, 0.85, 1.01, and 1.1 were systematically examined). As active knee flexion increased, PF contact force also increased. Patella alta (BP = 1.1) resulted in higher PF contact forces compared to normal patella height (BP = 0.65) by up to 16%. Contrarily, patella baja was associated with decreased PF forces by 7%. Compared to patella baja (BP = 0.39), patella alta (BP = 1.1) considerably increased the contact force by up to 25%. Different patellar heights mainly affected PF shear forces during early knee flexion. Concerning PF kinematics, patella alta (BP = 1.1) yielded a greater lateral tilt of more than 4° and higher patellar rotation by up to 3° during deep knee flexion, compared to normal patella height (BP = 0.65). Our computational study indicates that patella alta is associated with the highest PF contact and shear force after the implantation of a CR bicondylar TKA. This should be considered in PF disorders following TKA.

Association of patella alignment with cartilage relaxation times and self-reported symptoms in individuals with patellofemoral degeneration

To determine the cross-sectional and longitudinal associations of patella alignment with cartilage relaxation and patients' self-reported symptoms. Thirty participants with isolated patellofemoral joint (PFJ) degeneration (six males, 53.7 ± 9.3 years) and 24 controls (12 males, 47.6 ± 10.7 years) were included. Magnetic resonance assessment was performed to provide grading of structural abnormalities, cartilage relaxation times, and patella alignment. Self-reported symptoms were assessed using the self-administrated knee injury and osteoarthritis outcome score (KOOS). All participants were examined at baseline and 3 years. Statistical parametric mapping and Pearson partial correlation were used to evaluate the associations between patella alignment with cartilage relaxation times and self-reported symptoms, respectively. The analyses were performed between baseline (cross-sectional) as well as the baseline against 3 years (longitudinal). Results indicated that patella height and patella flexion were associated with T1ρ and T2 relaxation times at baseline (percentages of voxels showing significant correlation [PSV] = 10.1%-24.8%; mean correlations [R] = 0.34-0.36; mean p = 0.015-0.026). Furthermore, greater patella lateral alignment, lateral tilt, and lateral spin were associated with longer T2 times at 3 years (PSV = 11.0%-14.4%, R = 0.39-0.44, p = 0.017-0.028). Last, a higher patella was associated with a lower KOOS at baseline and at 3 years (R = -0.33 to -0.35). The study suggests that patella malalignment is a risk factor for worsening cartilage health, informing clinicians of a better rehabilitation program that targets PFJ degeneration.

Patella-Posterior Turning Point of the Distal Femur Distance Is a Potential Indicator for Diagnosing Patella Alta in Recurrent Patellar Dislocation Population

PURPOSE

To introduce a simple patellar height measurement method (patella-posterior turning point of the distal femur [P-PTP] Distance) independent of patellar anatomy with standardized patient position, and tested the reliability, validity, and diagnostic accuracy compared with commonly used ratios in knee extension.

METHODS

We retrospectively reviewed 418 computed tomography (CT) images of the knee joint in a group of patients who were diagnosed recurrent patellar dislocation (RPD). With the three-dimensional (3D) CT reconstructed knee, patellar height was qualitatively assessed by the patellar engagement with the femoral trochlea in terminal knee extension to divide RPD population into case (patella alta) and control group. With digitally reconstructed lateral radiographs, patellar height was measured with P-PTP distance (perpendicular distances between the distal edge of patella articular surface and posterior turning point of distal femur), and four commonly used ratios: Caton-Deschamps index, Modified Insall-Salvati index, Blackburne-Peel index, and Insall-Salvati index. An unpaired t-test was conducted to determine significant differences between groups. Correlation coefficient, intra- and inter-observer reliability, receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were also calculated.

RESULTS

198 knee images (198 patients) were included for final evaluation. Patella alta was present in 72 knees (36.3%) with RPD. The effect size was relatively large between the case and control group for P-PTP distance (d = -1.619; 95% CI, -1.948 to -1.286). P-PTP distance correlated moderately to strongly with four commonly used ratios (P < .001). Intraobserver and interobserver reliability was good for P-PTP distance. The AUC of the ROC curve was categorized as excellent for P-PTP distance, better than other measurements (P < .001), and the cutoff value was 4.2 mm with the highest sensitivity (86.11%) and specificity (84.92%).

CONCLUSIONS

The measurement method, P-PTP distance, showed good intra-observer and inter-observer reliability, well correlated with commonly used ratios, and presented best diagnostic accuracy among commonly used ratios for predicting RPD. P-PTP distance might be a potential indicator for identifying patella alta in RPD patients when supine and knee extended.

CLINICAL RELEVANCE

The measurement reported in this study may help in advancing clinical evaluation of patella alta, providing an alternative and simple method to measure patellar height. Standing or weight-bearing plain lateral radiographs obtained from the routine practice should be further assessed in the next step to further validate the method.

Patient-Reported Outcomes and Risk Factors for Decreased Improvement after Patellofemoral Arthroplasty

Patellofemoral arthroplasty (PFA) is acknowledged as the method for the treatment of isolated patellofemoral osteoarthritis (PFOA). Few previous studies have assessed the patient-reported outcomes (PROs) and risk factors of less improvement of PROs in patients undergoing PFA. A retrospective analysis was performed, including all patients who had undergone PFA. Pre- and postoperative PROs included the Oxford Knee Score (OKS) and Kujala score. Univariate and multivariate statistical analyses were performed to assess influencing factors of less improvement of PROs including the demographic factors (gender, age, body mass index, smoking, opioid usage, and duration of symptoms [DOSs]), surgical factors (concomitant surgery), and imaging factors (trochlear dysplasia [TD], patellar height, the degree of PFOA). A total of 46 PFAs were analyzed with a mean follow-up of 37 ± 7 months. The mean age at surgery was 61.1 ± 7.7 years. Patients showed significant improvement in all PROs (p < 0.001). Patients with TD preoperatively have greater improvement in OKS and Kujala score postoperatively (19.2 ± 5.0 vs. 23.1 ± 3.6, p = 0.038). Longer DOSs (≥1 year) had a greater mean improvement in OKS and Kujala score (p = 0.011 and p = 0.000). According to the measurement of patella height, patients with patella alta (Caton-Deschamps index [CDI] ≥1.3) showed less improvement in both OKS and Kujala score (p = 0.000 and p = 0.002). PFA is a safe and efficient surgery with good PROs. Patella alta with a CDI ≥1.3 and duration of preoperative symptoms ≤ 1 year were risk factors for decreased OKS and Kujala score improvement, while the preoperative presence of TD was significantly predictive factors for increased OKS improvement.

Patellotrochlea Index in Normal Healthy Knees

Patella alta is a common and significant abnormality responsible for many patellofemoral joint-related conditions. Many methods of patella height measurements are described; however, patellotrochear index (PTI) is the most logical method as it measures the direct relation between patella and trochlea. The aim of this study is to investigate PTI in normal healthy asymptomatic volunteers to understand the patellofemoral relation in normal knees. Twenty-five healthy volunteers underwent magnetic resonance imaging (MRI) scans of both knees. Two observers independently measured PTI on two different occasions at 6-week interval. Statistical analysis was performed to identify intra- and interobserver correlation between two observers and the mean value of PTI. Agreement analysis was performed according to Bland and Altman. Comparisons of means were made using paired t-tests. The mean age of 25 healthy volunteers was 21.28 years (19-23) with a male:female ratio of 14:11. The overall mean PTI value of all observations was 36.8% and pooled standard deviation (SD) 11.5%. Intraclass correlation (ICC) testing showed "good" interobserver ICC between two observers for PTI for both first (0.80) and second (0.84) set of measurements. There was "excellent" intraobserver correlation for two sets of measurements of PTI made by each first (0.96) and second (0.91) observer. Intraobserver repeatability for PTI was ± 0.07 and ± 0.1, respectively, for the first and second observer. Interobserver repeatability for PTI was ± 0.159 and ± 0.133, respectively, for the first and second set of measurements. Analysis of individual measurements of patella and trochlear articular cartilage revealed that the largest repeatability values were for trochlea measurements. The study reports that the average PTI in asymptomatic healthy knee utilizing current clinical MRI scanning conditions is 36.8%. This provides surgeons with a gold standard normal PTI value, which can serve as a target value in clinical diagnosis as well as surgical correction of patella height. There is good to excellent intra- and interobserver correlation with limited variability in assessing patella height using PTI on MRI scan.

Concurrent validity and reliability of a semi-automated approach to measuring the magnetic resonance imaging morphology of the knee joint in active youth

Post-traumatic knee osteoarthritis is attributed to alterations in joint morphology, alignment, and biomechanics triggered by injury. While magnetic resonance (MR) imaging-based measures of joint morphology and alignment are relevant to understanding osteoarthritis risk, time consuming manual data extraction and measurement limit the number of outcomes that can be considered and deter widespread use. This paper describes the development and evaluation of a semi-automated software for measuring tibiofemoral and patellofemoral joint architecture using MR images from youth with and without a previous sport-related knee injury. After prompting users to identify and select key anatomical landmarks, the software can calculate 37 (14 tibiofemoral, 23 patellofemoral) relevant geometric features (morphology and alignment) based on established methods. To assess validity and reliability, 11 common geometric features were calculated from the knee MR images (proton density and proton density fat saturation sequences; 1.5 T) of 76 individuals with a 3–10-year history of youth sport-related knee injury and 76 uninjured controls. Spearman’s or Pearson’s correlation coefficients (95% CI) and Bland-Altman plots were used to assess the concurrent validity of the semi-automated software (novice rater) versus expert manual measurements, while intra-class correlation coefficients (ICC2,1; 95%CI), standard error of measurement (95%CI), 95% minimal detectable change, and Bland-Altman plots were used to assess the inter-rater reliability of the semi-automated software (novice vs resident radiologist rater). Correlation coefficients ranged between 0.89 (0.84, 0.92; Lateral Trochlear Inclination) and 0.97 (0.96, 0.98; Patellar Tilt Angle). ICC estimates ranged between 0.79 (0.63, 0.88; Lateral Patellar Tilt Angle) and 0.98 (0.95, 0.99; Bisect Offset). Bland-Altman plots did not reveal systematic bias. These measurement properties estimates are equal, if not better than previously reported methods suggesting that this novel semi-automated software is an accurate, reliable, and efficient alternative method for measuring large numbers of geometric features of the tibiofemoral and patellofemoral joints from MR studies.

Treatment Options for Patellofemoral Arthritis

PURPOSE OF REVIEW

To present a synthesis of recent literature regarding the treatment of patellofemoral arthritis RECENT FINDINGS: Risk factors of PFJ OA include patella malalignment or maltracking, injury to supportive structures including the MPFL, dysfunction of hamstring and quadriceps coordination, lower limb alignment, trochlear dysplasia, patellar trauma, or ACL surgery. Special physical exam maneuvers include patellar grind test, apprehension test, and lateral patellar tilt angle. Radiographs that should be obtained first-line include weight bearing bilateral AP, lateral, and Merchant views. CT and MRI are used to assess trochlear dysplasia, excessive patellar height, and TT-TG distance. Non-operative management options discussed include non-pharmacologic treatment (patient education, self-management, physical therapy, weight loss), ESWT, cold therapy, taping, bracing, and orthotics. Pharmacologic management options discussed include NSAIDs, acetaminophen, oral narcotics, and duloxetine. Injection therapies include glucocorticoids, hyaluronic acid, PRP, and other regenerative therapies (BMAC, adipose, or mesenchymal stem cells). Other treatment options include radiofrequency ablation and botulinum toxin. The algorithm for the surgical treatment of PFJ OA can begin with arthroscopic assessment of the PF articular cartilage to address mechanical symptoms and to evaluate/treat lateral soft tissue with or without overhanging lateral osteophytes. If patients fail to have symptomatic improvement, a TTO can be considered in those patients less than 50 years of age or active patients >50 years old. In patients with severe PFJ OA, refractory to the above treatments, PFA should be considered. While early PFA design and technique were less than encouraging, more recent implant design and surgical technique have demonstrated robust results in the literature. Patellofemoral osteoarthritis is a challenging orthopedic problem to treat, in that it can often affect younger patients, with otherwise well-functioning knees. It is a unique entity compared to TF OA with distinct epidemiology, biomechanics and risk factors and treatment options.

Radiological evaluation of patellofemoral instability and possible causes of assessment errors

Patellofemoral instability (PI) is the disruption of the patella’s relationship with the trochlear groove as a result of abnormal movement of the patella. To identify the presence of PI, conventional radiographs (anteroposterior, lateral, and axial or skyline views), magnetic resonance imaging, and computed tomography are used. In this study, we examined four main instability factors: Trochlear dysplasia, patella alta, tibial tuberosity–trochlear groove distance, and patellar tilt. We also briefly review some of the other assessment methods used in the quantitative and qualitative assessment of the patellofemoral joint, such as patellar size and shape, lateral trochlear inclination, trochlear depth, trochlear angle, and sulcus angle, in cases of PI. In addition, we reviewed the evaluation of coronal alignment, femoral anteversion, and tibial torsion. Possible causes of error that can be made when evaluating these factors are examined. PI is a multi-factorial problem. Many problems affecting bone structure and muscles morphologically and functionally can cause this condition. It is necessary to understand normal anatomy and biomechanics to make more accurate radiological measurements and to identify causes. Knowing the possible causes of measurement errors that may occur during radiological measurements and avoiding these pitfalls can provide a more reliable road map for treatment. This determines whether the disease will be treated medically and with rehabilitation or surgery without causing further complications.

Strong Agreement Between Magnetic Resonance Imaging and Radiographs for Caton-Deschamps Index in Patients With Patellofemoral Instability

PURPOSE

To compare the measurements of the Caton-Deschamps index on preoperative magnetic resonance imaging and radiographs of patients undergoing operative management of patellar instability.

METHODS

Patients who underwent primary medial patellofemoral ligament reconstruction and/or tibial tubercle osteotomy between January 2015 and November 2019 were assessed. Caton-Deschamps indices were measured by 3 independent reviewers on both radiographs and magnetic resonance imaging. Intra- and interclass correlation coefficients and a Bland-Altman analysis were calculated to assess inter-rater reliability and measurement agreement between radiographic and magnetic resonance imaging.

RESULTS

Seventy-two patients (73 knees) were identified. The average Caton-Deschamps index was 1.23 ± 0.18 on radiograph and 1.26 ± 0.18 on magnetic resonance imaging. Strong inter-rater reliability was observed between reviewers for both radiographic and magnetic resonance imaging Caton-Deschamps indices (intraclass correlation coefficients 0.700 and 0.715, respectively). Pooled observer measurements revealed a moderate agreement between radiographic and magnetic resonance imaging for patella to tibia distance, weak agreement for patellar articular cartilage distance, and strong agreement for the Caton-Deschamps index (intraclass correlation coefficients 0.687, 0.485, and 0.749, respectively). Bland-Altman analysis demonstrated a mean difference in Caton-Deschamps index of -0.03 ± 0.15 (95% limits of agreement: -0.29 to 0.23) between radiographic and magnetic resonance imaging, meaning that Caton-Deschamps indices were on average 0.03 lower on radiographic than on magnetic resonance imaging.

CONCLUSIONS

The Caton-Deschamps index has strong agreement between radiographic and magnetic resonance imaging in patients undergoing patellar stabilization surgery. Either modality can be reliably used to preoperatively assess patellar height.

LEVEL OF EVIDENCE

Level IV, diagnostic case series.

Association of markers of patellofemoral maltracking to cartilage damage and bone marrow lesions on MRI: Data from the 2016 Olympic Games of Rio De Janeiro

Background

Patellofemoral joint (PFJ) disease is a common ailment in elite athletes. Our aim is to report the frequency of superolateral Hoffa’s fat pad (SHFP) edema, and PFJ cartilage damage and bone marrow lesions (BML), among Olympian athletes, and to study the association between measurements of trochlear morphology and vertical patellar position and a) PFJ cartilage damage or BML, and b) SHFP edema.

Methods

All knee MRI, performed in the Olympic Village and polyclinics, of participating athletes in the 2016 Olympic Games of Rio de Janeiro were included. MRI were scored for PFJ cartilage damage and BML, and SHFP edema. Trochlear morphology measurements included sulcus angle, trochlear angle, lateral trochlear inclination, and medial trochlear inclination. Insall-Salvati ratio was also assessed.

Results

One hundred twenty-one knee MRIs were included (62 female, 51.2 %). The highest frequencies of PFJ cartilage damage, combination of PFJ cartilage damage and BML, and SHFP edema were found among Beach Volleyball and Volleyball athletes. SHFP edema was more common among female compared to male Olympian athletes. We found no statistically significant associations between different measurements of trochlear morphology/vertical patellar position, and 1. SHFP edema, and 2. PFJ cartilage damage/BML.

Conclusion

SHFP edema and the combination of PFJ cartilage damage and BML are highly frequent among Olympic athletes especially those competing in Beach volleyball and Volleyball. SHFP edema is more common among female athletes. Further studies are needed to determine whether PFJ cartilage damage has a stronger association to sports disciplines rather than trochlear morphology.

Association of patellofemoral morphology and alignment with the radiographic severity of patellofemoral osteoarthritis

Background

Risk factors for the severity of patellofemoral osteoarthritis (PFOA) are poorly understood. This research aims to evaluate the association between patellofemoral joint (PFJ) morphology and alignment with the radiographic severity of PFOA.

Methods

A retrospective analysis of CT scan and lateral radiograph data were acquired in patients with PFOA. The radiographic grade of PFOA and tibiofemoral osteoarthritis (TFOA), lateral and medial trochlear inclination angle, sulcus angle, and the Wiberg classification of patella morphology, the congruence angle, patellar tilt angle, and lateral patellar angles, and tibial tubercle trochlear groove distance (TT-TG) and patella height (i.e., Caton-Deschamps index) were assessed using CT scans and sagittal radiographs of the knee. All the PFJ morphology and alignment data were divided into quarters, and the relationships between each of these measures and the severity of PFOA were investigated.

Results

By studying 150 patients with PFOA, we found a U-shaped relationship between the Caton-Deschamps index and the severity of PFOA (P < 0.001). A lower value of sulcus angle and lateral patellar angle, a higher value of congruence angle, and type III patella were associated with more severity of lateral PFOA. Compared with the highest quarter of each measure, the adjusted odds ratios (OR) of the severity of PFOA in the lowest quarter of sulcus angle, lateral patellar angle, and congruence angle; and type I patella was 8.80 (p = 0.043), 16.51 (P < 0.001), 0.04 (P < 0.001), and 0.18 (p = 0.048) respectively.

Conclusions

Extreme value of patella height, a higher value of lateral patellar displacement and lateral patellar tilt, lower value of sulcus angle, and type III patella were associated with more severity of PFOA.

Patella Apex Influences Patellar Ligament Forces and Ratio

The relationship between three-dimensional shape and patellofemoral mechanics is complicated. The Wiberg patella classification is a method of distinguishing shape differences in the axial plane of the patella that can be used to connect shape differences to observed mechanics. This study uses the Wiberg patella classification to differentiate variance in a statistical shape model describing changes in patella morphology and height. We investigate how patella morphology influences force distribution within the patellofemoral joint. The Wiberg type I patella has a more symmetrical medial and lateral facet while the type III patella has a larger lateral facet compared to medial. The second principal component of the statistical shape model described shape variation that qualitatively resembled the different Wiberg patellas. We generated patellofemoral morphologies from the statistical shape model and integrated them into a musculoskeletal model with a twelve degrees-of-freedom knee. We simulated an overground walking trial with these morphologies and recorded patellofemoral mechanics and ligament forces. An increase in patellar ligament force corresponded with an increase in patella height. Wiberg type III patellas had a sharper patella apex which related to lower ratios of quadriceps tendon forces to patellar ligament forces. The change in pivot point of the patella affects the ratio of forces as well as the patellofemoral reaction force. This study provides a better understanding of how patella morphology affects fundamental patella mechanics which may help identify at-risk populations for pathology development.

Clinical Improvement Is Achieved Following Tibial Tubercle Distomedialization for Patellar Maltracking and Patella Alta Without Instability

Purpose

To determine short-term patient-reported outcomes following distomedial tibial tubercle transfer (TTT) in patients with patellar maltracking and patella alta without instability.

Methods

A single-surgeon case series study was performed on patients receiving distomedial TTT for the indication of patellar maltracking and patella alta without instability, after nonresponse to conservative treatment. Patient-reported outcomes were assessed preoperatively and at 3-, 6-, 12-, and 24-month follow-up using Kujala, Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analog scale (VAS) pain scores. Generalized estimating equations analyses were performed to study improvement over time. Minimal clinically important differences obtained from literature were used to determine clinical relevance.

Results

A total of 40 patients were included. Eight patients were lost to follow-up; thus, outcomes of 32 patients were analyzed. Mean follow-up was 22 months, median age was 21 years, and 75% were female. Mean Kujala score increased pre- to postoperatively from 55 ± 12 to 79 ± 16 (P < .001), KOOS from 48 ± 14 to 79 ± 15 (P < .001), and VAS from 64 ± 17 to 25 ± 21 (P < .001), respectively. Eighty-four percent had clinical improvement of Kujala score, 91% of KOOS, and 78% of VAS score. A plateau phase in pain reduction was reached at 3 months, and in functional improvement at 6 months follow-up, after which no further significant improvement was observed. Complication rate was 3% and removal of hardware rate was 72%. Conclusions: In this case series study, distomedial TTT led to clinically relevant functional improvement and pain reduction in patients with patellar maltracking and patella alta without instability. However, the removal of hardware rate was high (72%).

Level of Evidence

Level IV, therapeutic case series.

Tibial tubercle transfer leads to clinically relevant improvement in patients with patellar maltracking without instability: a systematic review and meta-analysis

PURPOSE

To assess the different surgical techniques and their outcomes following tibial tubercle transfer (TTT) in patients with patellar maltracking.

METHODS

A systematic search of the literature was performed in PubMed, EMBASE and Cochrane Library. Studies reporting patient-reported outcome measures (PROMs) or clinical outcome following: TTT in patients with patellar maltracking were included. Collected PROMs were Lysholm, Kujala, IKDC score, and VAS pain. Clinical outcome included reported clinical success, patient satisfaction, complications and removal of hardware (ROH). Overall pre-, post-operative and change scores were estimated using random-effects meta-analysis models. Results were reported as overall mean and per transfer direction.

RESULTS

A total of 26 studies and 761 patients (818 knees, mean age 35 years, mean follow-up 5.0 years) were included. In 73% of the studies, surgery was performed after failed conservative treatment. Transfer direction was anteromedial in 76% of all procedures. Overall Lysholm score improved from 61 to 91, Kujala from 52 to 85, IKDC from 53 to 81, and VAS from 6.2 to 2.5, respectively. Clinical success was reported in 79% of patients, and 80% of patients reported to have satisfactory results. Rates of complications and ROH were 13% and 29%, respectively.

CONCLUSIONS

TTT for management of patellar maltracking can lead to good results with clinically meaningful improvement, an overall clinical success of 79% and overall patient satisfaction of 80% when appreciating the underlying anatomic condition and using appropriate technique. The level of evidence was low, and large-scale prospective, comparative cohort studies with uniform outcome scales are needed to confirm these findings.

LEVEL OF EVIDENCE

IV.

Moment arm function dictates patella sagittal height anatomy: Rabbit epiphysiodesis model alters limb length ratios and subsequent patellofemoral anatomical development

Patellofemoral anatomical dysplasia is associated with patellofemoral instability and pain. The closure of the knee physis occurs at the same age as the peak incidence of patellofemoral dislocation. This study determined the effect on the patellofemoral anatomical development in a rabbit epiphysiodesis model. Twenty-four skeletally immature New Zealand White rabbits were divided into three groups (a) distal femur epiphysiodesis (FE) (b) proximal tibia epiphysiodesis (TE) (c) control; no epiphysiodesis (C) performed at 6 weeks of age. The primary endpoint was shape analysis using three-dimensional reconstructions of micro-computed tomographys (CTs) performed at 30 weeks of age. The limb length ratios (femur:tibia) were significantly different for both FE (mean 0.72, SD 0.0381, P < .001) and TE (mean 0.91, SD 0.0383, P < .001) treatment groups compared to control (mean 0.81, SD 0.0073). Patella height, as measured from the most distal point of the patella to the tibial joint surface (modified Caton-Deschamps measurement), was lower (baja) in the FE and higher (alta) for the TE, compared with the control group. Our findings suggest femoral and tibial shortening can influence the development of the patellofemoral joint, which may be dictated by moment arm function and is potentially responsible for the etiology of patella alta. Future studies are warranted to explore this association further with the view for the development of treatment options for patella alta in human patients.

Patella Height as Defined by Patella-Trochlear Articulation on MRI Scan-A Systemic Review of Current Evidence

The objective of this study is to investigate what are the normal values, cutoff values, and optimal method of magnetic resonance imaging (MRI) scan for patella height focusing on patella-trochlear index (PTI). Electronic searches of MEDLINE (PubMed), Cumulative Index to Nursing and Allied Health Literature, Cochrane, Embase, ScienceDirect, and National Institute for Health and Care Excellence evidence up to April 2018 were completed. Eligibility criteria for selected studies included case-controlled studies, prospective cohort studies, cross-sectional and randomized controlled trials reporting on the use of MRI to evaluate direct patella height. Exclusions included animal or biomechanical/computational studies; interventional surgery such as knee arthroplasty, bracing, or realignment; and hereditary/congenital disease. A quality assessment of included studies was completed using the Methodological Index for Non-Randomized Studies (MINORS) Criteria. Sixty-four articles were identified which met the inclusion criteria. Following exclusions, 11 full-text studies were reviewed which reported direct measure of patella height. Nine studies reported the use of PTI. Two low power studies described PTI in normal healthy asymptomatic knee. Similarly, one study evaluated the effect of flexion and weight bearing on PTI values. The cutoff values varied between studies from <0.125 to <0.28 for patella alta and >0.50 to >0.80 for patella baja. This review found that currently, there are a very few studies on the assessment of PTI on MRI scan, with only two low powered studies on a true normal population. In view of this, there is a need for adequately powered studies to investigate patella height and PTI in asymptomatic healthy knees.

Patellar Tendon Imbrication Is a Safe and Efficacious Technique to Shorten the Patellar Tendon in Patients With Patella Alta

Background

Patella alta has been noted to be a risk factor for recurrent patellar instability.

Purpose

We conducted a radiographic study to determine whether a patellar tendon imbrication technique normalizes patellar height as well as whether the shortened length is maintained at a minimum 2-year follow-up.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 54 consecutive patients were identified after a retrospective chart review was performed on patients who underwent patellar tendon imbrication between 2008 and 2013. Preoperative, 3 weeks postoperative, and minimum 2 years postoperative lateral radiographs were analyzed using Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) indices to determine the amount of shortening that was achieved after the procedure and to what degree that shortening was maintained at a minimum 2-year follow-up.

Results

A total of 27 patients (32 knees) completed a minimum 2-year follow-up. The mean patellar tendon length preoperatively was 6.1 cm (range, 5-8 cm). At 3 weeks and 2 years, the mean tendon lengths were 5.1 and 5.2 cm, respectively. Thus, the mean ± SD change in patellar tendon length from preoperative to 3 weeks postoperative was 0.97 ± 0.67 cm. IS, BP, and CD ratios had minimal change (loss of correction) from 3-week to 2-year follow-up; the delta values were 0.04, -0.03, and 0.09, respectively. There were no complications directly related to the technique.

Conclusion

Patellar tendon imbrication is a safe and effective procedure to correct patella alta in the setting of lateral patellar instability. On average, the technique allowed 1 cm of patellar tendon shortening and maintained the correction at a minimum 2-year follow-up. In the skeletally immature patient, this technique allows correction of patella alta by avoidance of a tibial tuberosity osteotomy.

Zone- and layer-specific differences in proteoglycan content in patellofemoral pain syndrome are detectable on T1ρ MRI

OBJECTIVE

Determine if differences in T1ρ would be detected in specific regions or layers of patellofemoral cartilage between patients with symptomatic patellofemoral pain syndrome and asymptomatic control subjects.

MATERIALS AND METHODS

Ten subjects diagnosed with patellofemoral pain syndrome were compared with ten age-, gender-, and BMI-matched control subjects with no knee pain or prior trauma. Conventional turbo (fast) spin echo sequences and T1ρ-weighted imaging were performed on the symptomatic knee in each of the ten subjects. At the patella and distal femur, cartilage regions of interest were divided into medial and lateral sub-regions, each then further sub-divided by layer (superficial, middle, or deep). Two-tailed t test and chi-squared tests were used to analyze demographic data. A mixed effect model was run for each sub-region of T1ρ imaging. Statistical significance was determined using the likelihood ratio test against reduced models without patellofemoral pain syndrome symptomatic status as a fixed effect.

RESULTS

There was no difference in age, sex, or BMI between symptomatic and control patients. T1ρ values were significantly higher among patellofemoral pain syndrome patients when compared with controls in the superficial zone of the lateral patella (58.43 vs. 50.83, p = 0.03) and the middle zone of the lateral patella (52.67 vs. 43.60, p = 0.03). T1ρ was also higher in the superficial zone of the medial femur (50.94 vs. 46.70, p = 0.09) with a value approaching statistical significance.

CONCLUSION

We report statistically significant differences in the T1ρ value in the superficial and middle zones of the lateral patella in patients with patellofemoral pain syndrome who had no abnormalities seen on conventional MRI sequences, suggesting an alteration the macromolecular structure of the cartilage in this population.

Association between increased signal intensity at the proximal patellar tendon and patellofemoral geometry in community-based asymptomatic middle-aged adults: a cross-sectional study

BACKGROUND

Histological and epidemiological data suggest that increased signal intensity at the proximal patellar tendon on magnetic resonance imaging is a response to tendon loading. As patellofemoral geometry is a mediator of loading, we examined the association between patellofemoral geometry and the prevalence of increased signal intensity at the patellar tendon in community-based middle-aged adults.

METHODS

Two hundred-one adults aged 25-60 years in a study of obesity and musculoskeletal health had the patellar tendon assessed from magnetic resonance imaging. Increased signal intensity at the proximal patellar tendon was defined as hyper-intense regions of characteristic pattern, size and distribution on both T1- and T2-weighted sequences. Indices of patellofemoral geometry, including Insall-Salvati ratio, patellofemoral congruence angle, sulcus angle, and lateral condyle-patella angle, were measured from magnetic resonance imaging using validated methods. Binary logistic regression was used to examine the association between patellofemoral geometrical indices and the prevalence of increased signal intensity at the patellar tendon.

RESULTS

The prevalence of increased signal intensity at the patellar tendon was 37.3%. A greater Insall-Salvati ratio (odds ratio 0.80, 95% confidence interval 0.66-0.97 per 0.1 change in the ratio, p = 0.02), indicative of a higher-riding patella, and a larger patellofemoral congruence angle (odds ratio 0.91, 95% confidence interval 0.85-0.98 per 5 degree change in the angle, p = 0.01), indicating a more laterally placed patella, were associated with reduced odds of increased signal intensity at the patellar tendon. Sulcus angle and lateral condyle-patella angle were not significantly associated with the odds of increased signal intensity at the patellar tendon.

CONCLUSIONS

In community-based asymptomatic middle-aged adults, increased signal intensity at the patellar tendon was common and associated with Insall-Salvati ratio and patellofemoral congruence angle, suggesting a biomechanical mechanism. Such work is likely to inform tissue engineering and cell regeneration approaches to improving outcomes in those with tendon pathology.

Relation of Patellofemoral Joint Alignment, Morphology, and Radiographic Osteoarthritis to Frequent Anterior Knee Pain: Data from the Multicenter Osteoarthritis Study

OBJECTIVE

Patellofemoral (PF) alignment and trochlear morphology are associated with PF osteoarthritis (OA) and knee pain, but whether they are associated with localized anterior knee pain is unknown, which is believed to be a symptom specific to PF joint pathology. We therefore aimed to evaluate the relation of PF alignment and morphology, as well as PFOA and tibiofemoral OA, to anterior knee pain.

METHODS

The Multicenter Osteoarthritis Study is a cohort study of individuals with, or at risk for, knee OA. We evaluated cross-sectional associations of PF alignment, trochlear morphology, and PF and tibiofemoral radiographic OA, with localized anterior knee pain (defined with a pain map). We used 2 approaches: a within-person knee-matched evaluation of participants with unilateral anterior knee pain (conditional logistic regression), and a cohort approach comparing those with anterior knee pain to those without (binomial regression).

RESULTS

With the within-person knee-matched approach (n = 110; 64% women, mean age 70 years, body mass index [BMI] 30.9), PF alignment, morphology, and tibiofemoral OA were not associated with unilateral anterior knee pain. Radiographic PFOA was associated with pain, odds ratio 5.3 (95% confidence interval [95% CI] 1.6-18.3). Using the cohort approach (n = 1,818; 7% of knees with anterior knee pain, 59% women, mean age 68 years, BMI 30.4), results were similar: only PFOA was associated with pain, with a prevalence ratio of 2.2 (95% CI 1.4-3.4).

CONCLUSION

PF alignment and trochlear morphology were not associated with anterior knee pain in individuals with, or at risk for, knee OA. Radiographic PFOA, however, was associated with pain, suggesting that features of OA, more so than mechanical features, may contribute to localized symptoms.

Associations of trochlea morphology and patellofemoral alignment with prevalent radiographic patellofemoral osteoarthritis

OBJECTIVE

To investigate the relation of trochlea morphology and patellofemoral alignment to prevalent radiographic patellofemoral osteoarthritis (PFOA).

DESIGN

A within-person knee-matched case-control study was performed. Participants with unilateral radiographic PFOA were selected from the Multicenter Population-based Osteoarthritis Study (MPOA) in three towns in northern China that was approved by Peking University Health Science Center Ethics Committee (2018PHB166-01). Radiographic PFOA, radiographic tibiofemoral OA, sulcus angle, patellofemoral index and patella displacement were assessed using posterio-anterior and skyline views of the knee. We classified sulcus angle, patellofemoral index and patella displacement into quarters and investigated the relation of each of these measures to prevalent radiographic PFOA.

RESULTS

Among 451 participants (mean age: 65.2 years, women: 66.8%) with unilateral radiographic PFOA, a reverse J-shaped relationship was observed between sulcus angle and prevalent radiographic PFOA (P = 0.039 for quadratic term). Both higher patellofemoral index and patella displacement were associated with higher prevalent radiographic PFOA. Adjusted odds ratios (ORs) of prevalent radiographic PFOA in the highest quarter of patellofemoral index and patella displacement were 4.69 and 3.60 (P for trend <0.001), respectively, compared with the lowest quarter of each measurement. A similar relationship was observed between sulcus angle with either prevalent radiographic lateral or medial PFOA. Higher values of patellofemoral index and patella displacement were statistically significantly associated with higher prevalent radiographic lateral (ORs = 5.07 and 4.59, respectively), but not medial PFOA (ORs = 0.58 and 0.76, respectively).

CONCLUSION

Extreme sulcus angles as well as higher values of patellofemoral index and patella displacement were associated with higher prevalent radiographic PFOA.

Patellofemoral Mechanics: a Review of Pathomechanics and Research Approaches

PURPOSE OF REVIEW

The patellofemoral joint is a complicated articulation of the patella and femur that is prone to pathologies. The purpose of this review is to report on the current methods of investigating patellofemoral mechanics, factors that affect joint function, and future directions in patellofemoral joint research with emerging technologies and techniques.

RECENT FINDINGS

While previous hypotheses have suggested that the patella is only a moment arm extender, recent literature has suggested that the patella influences the control of knee moments and forces acting on the tibia as well as contributes to various aspects of patellar function with minimal neural input. With advancements in simulating a six-degrees-of-freedom patellofemoral joint, we have gained a better understanding of patella motion and have shown that geometry and muscle activations impact patella mechanics. Research into influences on patella mechanics from other joints such as the hip and foot has become more prevalent. In this review, we report current in vivo, in vitro, and in silico approaches to studying the patellofemoral joint. Kinematic and anatomical factors that affect patellofemoral joint function such as patella alta and tilt or bone morphology and ligaments are discussed. Moving forward, we suggest that advanced in vivo dynamic imaging methods coupled to musculoskeletal simulation will provide further understanding of patellofemoral pathomechanics and allow engineers and clinicians to design interventions to mitigate or prevent patellofemoral pathologies.

Patellofemoral alignment and geometry and early signs of osteoarthritis are associated in patellofemoral pain population

Background

Patellofemoral pain (PFP) patients show increased prevalence of patellar malalignment. Structural and alignment abnormalities of the patellofemoral joint (PFJ) may play a role in development of PFP and patellofemoral osteoarthritis (PFOA).

Objectives

Evaluating associations of patellofemoral alignment and femoral geometry with bony and cartilaginous abnormalities in PFP patients and healthy control subjects.

Methods

Data from a case‐control study were used (64 PFP subjects, 70 control subjects, 57% female, age 23.2 (6.4)). Alignment and femoral geometry measures in the PFJ were determined using MRI. Structural abnormalities in the PFJ associated with OA (bone marrow lesions, osteophytes, minor cartilage defects and Hoffa‐synovitis), quantified cartilage composition (T1ρ relaxation times) in the PFJ and perfusion within the patellar bone were examined using different MRI techniques. Associations were analyzed using regression analyses, adjusted for potential confounders.

Results

Lateral patellar tilt was negatively associated with presence of osteophytes on both patella (OR 0.91; 95% CI 0.84 to 0.98), anterior femur (OR 0.92; 95% CI 0.84 to 0.99) and minor cartilage defects on patella (OR 0.91; 95% CI 0.84 to 0.99). Patella alta was positively associated with the presence of bone marrow lesions in the patella and minor cartilage defects (OR 48.33; 95% CI 4.27 to 547.30 and OR 17.51; 95% CI 1.17 to 262.57, respectively). Patella alta and medial patellar translation were positively associated with T1ρ relaxation times within trochlear cartilage (β 5.2; 95% CI 0.77 to 9.58, and 0.36; 95% CI 0.08 to 0.64, respectively). None of the alignment and geometry measures were associated with bone perfusion.

Conclusion

Our study implies that associations between patellofemoral alignment and geometry and structural joint abnormalities linked to OA are already present in both PFP patients and healthy control subjects.

Sharp margin of antero-inferior lateral femoral condyle as a risk factor for patellar tendon-lateral femoral condyle friction syndrome

OBJECTIVE

To determine the correlation between patellar tendon-lateral femoral condyle friction syndrome (PLFFS) and the morphological characteristics of the antero-inferior part of the lateral femoral condyle (ALFC) to explore the potential pathogenesis.

METHODS

A total of 170 knees of 140 patients with PLFFS (PLFFS group) were retrospectively analyzed using magnetic resonance imaging (MRI) data for a 4-year period from our database. The Insall-Salvati ratio, shape of the ALFC (SALFC, defined as two subtypes: sharp versus blunt), lateral femoral condyle angle (LFCA), lateral trochlear length (LTL), and lateral trochlear height (LTH) were measured on MRI. Two groups were enrolled as controls: pure patella alta group (n = 192) and normal group (n = 172). All the parameters of the PLFFS group were compared with those of the two control groups.

RESULTS

The LFCA was significantly lower (p < 0.001) in the PLFFS group than in the pure patella alta group. The SALFC was significantly different (p < 0.001) in these two groups, whereas the Insall-Salvati ratio, LTH, and LTL showed no significant difference. The LFCA, LTH, SALFC, and the Insall-Salvati ratio in the PLFFS group were also significantly different (p < 0.001) with the normal group. Receiver operating characteristic (ROC) analysis showed the efficacy of the Insall-Salvati ratio and SALFC was better than that of the other parameters.

CONCLUSIONS

The morphological characteristics of ALFC are correlated with PLFFS. The sharp shape of ALFC may be an important causative co-factor along with patella alta in the pathogenesis of PLFFS.

KEY POINTS

• A sharp margin of the antero-inferior lateral femoral condyle is an important risk factor for the development of PLFFS in patients with patella alta. • Antero-inferior femoral condyle shape can easily be assessed with high intra- and inter-reader reliability PLFFS. • PLFFS is more common in young adults.

Patellofemoral morphology measurements and their associations with tibiofemoral osteoarthritis-related structural damage: exploratory analysis on the osteoarthritis initiative

OBJECTIVES

Given the coexistence and possible interactions between patellofemoral and tibiofemoral compartments, roles of patellofemoral morphology measurements in tibiofemoral osteoarthritis (OA) have not been investigated extensively. We aimed to determine whether patellofemoral morphology is associated with the presence and longitudinal worsening of tibiofemoral OA in participants of the Osteoarthritis Initiative (OAI).

METHODS

Baseline knee MRIs of 600 participants were read by two independent blinded observers in consensus to determine patellofemoral morphology measurements including tibial tuberosity to trochlear groove (TT-TG) distance, trochlear groove depth (TGD), lateral patellar tilt (LPT), and Insall-Salvati ratio (ISR). Radiographic and MRI OA knee scoring (MOAKS) measurements were extracted from baseline and 2-year follow-up readings. Associations between baseline patellofemoral morphology metrics with radiographic medial tibiofemoral compartment (MTFC) joint space loss (> 0.7 mm, between baseline and 2nd-4th-year readings), and MRI-derived cartilage damage, bone marrow lesions (BMLs), and osteophytes (baseline to 2 years), were investigated using regression models adjusted for age, sex, body mass index, and knee alignment. P values were corrected using the Benjamini-Hochberg procedure.

RESULTS

Patellofemoral morphology measurements were not associated with longitudinal joint space loss in the MTFC or MOAKS determinants. Only TT-TG distance was associated with the baseline number of subregions with cartilage defects (OR (95% CI), 1.09 (1.04-1.14), corrected p value ≤ 0.01), BMLs (OR (95% CI), 1.1 (1.04-1.17), corrected p value = 0.01), and osteophytes (OR (95% CI), 1.09 (1.05-1.14), corrected p value ≤ 0.01) in the lateral tibiofemoral compartment (LTFC), and worsening of LTFC cartilage defects over 2 years (OR (95% CI), 1.09 (1.03-1.16), corrected p value = 0.02).

CONCLUSIONS

Higher TT-TG distance was associated with concurrent MRI-derived OA-related structural damages and 2-year follow-up worsening only in LTFC. No associations were detected between patellofemoral morphology measurements and MTFC OA progression.

KEY POINTS

• Of all patellofemoral morphology measurements, the only lateralization of the tibial tubercle may be considered as a risk factor for lateral (not medial) tibiofemoral osteoarthritis worsening. • Patellofemoral morphology measurements of patella alta, trochlear dysplasia, patellar tilt, and lateralization of the tibial tubercle are not associated with radiographic and MRI-based medial tibiofemoral osteoarthritis worsening over 2 years. • Using longitudinal MRI data, each millimeter increase of TT-TG distance is associated with a 9% (95% confidence interval, 3-16%) increase in odds of longitudinal cartilage defects in the lateral tibiofemoral (but not medial) compartment over 2 years.

Superolateral Hoffa's fat pad oedema: Relationship with cartilage T2* value and patellofemoral maltracking

PURPOSE

To determine (1) the association between superolateral Hoffa's fat pad (SHFP) oedema and early cartilage degeneration using T2* mapping and (2) whether patellofemoral maltracking is related to cartilage T2* values or SHFP oedema.

MATERIALS AND METHODS

In this retrospective study, 68 patients (71 knees) with anterior knee pain who had undergone 3-Tesla magnetic resonance imaging (MRI) were enrolled. Cartilage T2* values in medial and lateral patellofemoral compartment as well as patellofemoral maltracking parameters (trochlear angle, sulcus angle, patellar tilt angle, tibial tuberosity-to-trochlear groove [TT-TG] distance, and patellar-tendon to patellar-length [PT-PL] ratio) were compared between case group (24 knees with SHFP oedema) and control group (47 knees without the oedema). The associations between the patellofemoral maltracking and the cartilage T2* values as well as the SHFP oedema were investigated using logistic and linear regression analyses.

RESULTS

The case group showed significantly higher cartilage T2* value in the lateral patellar facet, wider sulcus angle, greater TT-TG distance, and higher PT-PL ratio than the control group. Both SHFP oedema and higher cartilage T2* value in the lateral patellar facet were significantly associated with wider sulcus angle, greater TT-TG distance, and higher PT-PL ratio.

CONCLUSION

SHFP oedema appears to be associated with inherent cartilage degeneration in the lateral patellar facet. Patellofemoral maltracking might be a risk factor for SHFP oedema and early cartilage damage in the lateral patellar facet.

[Combined operation involving tibial tubercle distalization for recurrent patellar dislocation with patella alta]

Objective

To explore the clinical effects of combined operation involving tibial tubercle distalization for the recurrent patellar dislocation with patella alta.

Methods

Between April 2010 and May 2016, 14 cases of recurrent patellar dislocation with patella alta were treated with combined operation involving tibial tubercle distalization. There were 5 males and 9 females with an average age of 18.5 years (range, 13-26 years). The left knee was involved in 9 cases and the right knee in 5 cases. The patella had dislocated 3.3 times on average (range, 2-5 times). The interval between the first dislocation and admission was 19.7 months on average (range, 4-60 months), and the main symptoms were knee pain and limited knee movement. Preoperative X-ray films, CT, and MRI examinations of knee joint showed that the epiphyseal plate closed in all patients. Of all patients, 3 patients had avulsion fracture of the inner edge of patella, and 2 patients had free body in articular cavity. The tibial tuberosity-trochlear groove (TT-TG) distance, patellar-trochlear-groove distance, Caton-Deschamps index, knee range of motion (ROM), Lysholm score, International Knee Documentation Committee (IKDC) score, Kujala score, and Tegner score were compared pre- and post-operation.

Results

All patients had primary wound healing. All patients were followed up 24-72 months with an average of 34.6 months. X-ray film and CT examination showed that the patellar dislocation was corrected and the osteotomy of the tibial tubercle healed with an average healing time of 3.8 months (range, 3-5 month). At 1 day and 1 year after operation, the TT-TG distance, patellar-trochlear-groove distance, and Caton-Deschamps index showed significant differences when compared with preoperative values ( P<0.05), but there was no significant difference between 1 day and 1 year after operation ( P>0.05). At the 1 year and 2 years after operation, the knee ROM, Lysholm score, IKDC score, Kujala score, and Tegner score showed significant differences when compared with preoperative values ( P<0.05), and there was no significant difference between the 1 year and 2 years after operation ( P>0.05).

Conclusion

Combined operation involving tibial tubercle distalization is a safe and reliable method, which has satisfactory short-term effectiveness for the recurrent patellar dislocation with patella alta.

Influence of Patella Height on Total Knee Arthroplasty: Outcomes and Survival

BACKGROUND

The aim of this study is to assess clinical results of total knee arthroplasty (TKA) with pre-operative patella alta or patella baja, compared to TKA with pre-operative normal patellar height.

METHODS

Patella height was measured using the Blackburne-Peel (BP) method in an initial, prospective cohort of 4103 TKAs performed at a single center. Three groups were defined: normal patella height (0.54 < BP index ≤ 1.06), patella alta (BP index >1.06), and patella baja (BP index ≤0.54). Pre-operative and post-operative clinical and radiological characteristics were collected and compared. All prostheses used a system of posterior stabilization by a third condyle. The primary outcome measure was the post-operative Knee Society Score. Statistical analysis was performed using Student's t-test and chi-squared test, with P < .05.

RESULTS

Two hundred twenty-three TKAs with pre-operative patella alta, 307 TKAs with pre-operative patella baja, and 2248 with pre-operative normal patella height, mean follow-up 39.3 months (range 24-239), were ultimately included. Post-operatively, there was no difference between the 3 groups in terms of Knee Society Score (knee and function scores). Patella baja statistically decreased the maximal flexion (118.2° vs 115.5°, P = .002) and increased the rate of patellar fracture (0.9% vs 2%, P = .05). Finally, survival rates were similar in the 3 groups with each above 91% (±2%) at 10 years.

CONCLUSION

Clinical and radiological results for TKAs with pre-operative patella alta and patella baja were comparable to TKAs with a normal pre-operative patellar height. Risk of post-operative patellar fracture increased for patients with pre-operative patella baja.

Association of patella alta with worsening of patellofemoral osteoarthritis-related structural damage: data from the Osteoarthritis Initiative

OBJECTIVES

To determine the association between Insall-Salvati ratio (ISR), a measure of patella alta, and worsening of Magnetic Resonance Imaging (MRI)-based osteoarthritis (OA)-related patellofemoral joint structural damages over 24-month in participants of the Osteoarthritis Initiative (OAI).

DESIGN

Using weighted random sampling method, we selected a sample of 500 knees (from 1,677 knees with available baseline and 24-months MRI OA Knee Score (MOAKS) measurements), which is OAI-representative regarding knee OA-related factors (i.e., baseline age, sex, body mass index (BMI), and radiographic Kellgren-Lawrence grading). The ISR was measured in all enrolled knees using baseline sagittal 3T-MRI plane by three radiologists. Baseline and 24-month MOAKS variables for patellofemoral bone marrow lesions (BMLs), cartilage damages, and osteophytes were extracted, and the associations between ISR and 24-month worsening of these 3T-MRI features were evaluated using multivariable regression models. After computing receiver operating characteristic curves, the optimal cutoff point of ISR for indicating worsening of patellofemoral OA was determined. P-values were adjusted for multiple comparisons and false discovery rate (FDR) adjusted P-values were reported.

RESULTS

In this longitudinal analysis, 24-month worsening of BML (odds ratio [OR] (95% confidence interval [95% CI]):11.18 (3.35-39.6), adjusted-p-value:<0.001) and cartilage scores (OR:7.39 (1.62-34.71), adjusted-p-value:0.042) in lateral patella was associated with higher baseline ISR. However, higher ISR was not statistically associated with medial patellar or medial and lateral trochlear BML or cartilage scores worsening. We determined the optimal cutoff point of ISR≥1.14 (95% CI: 1.083-1.284) for predicting lateral patellofemoral OA-related structural damages worsening over 24-months (sensitivity:73.73%; specificity: 66.67%).

CONCLUSIONS

Given the uncertainly surrounding the results, our overall findings suggest that ISR could be considered as a predictor of lateral patellofemoral OA-related structural damages worsening with the optimal cutoff point of ≥1.14 using knee sagittal MRI measurements.

Histopathological changes in the infrapatellar fat pad in an experimental rabbit model of early patellofemoral osteoarthritis

BACKGROUND

The purpose of this study was to characterise the histopathological changes in the infrapatellar fat pad (IPFP) in the early stage of patellofemoral osteoarthritis (PFOA).

METHODS

Sixty-four New Zealand white rabbits were randomly divided into experimental (n = 24), sham (n = 16), and control groups (n = 24). In the experimental group, denoted as the patellar ligament uneven shortening group (US group), the patellar ligament (PL) was folded eight millimetres and sutured. After eight weeks, all animals were euthanised, and magnetic resonance imaging (MRI) evaluation, wet IPFP weight measurement, and histopathological and immunohistochemistry analysis were performed to analyse the histopathological changes in the IPFPs.

RESULTS

The maximum cross-sectional area (CSA) of the IPFPs in the sagittal position of MRI in the control group, sham group, and US group were 45.50 ± 7.19 mm², 45.88 ± 6.60 mm² (vs. control group, P = 0.907), and 53.83 ± 8.24 mm² (vs. control group, P = 0.015; vs. sham group, P = 0.035), respectively. The MRI intensity of the IPFPs in the control group, sham group, and US group were 115.53 ± 28.85, 108.53 ± 26.73 (vs. control group, P = 0.589), and 154.52 ± 18.48 (vs. control group, P = 0.002; vs. sham group, P = 0.002), respectively. The wet weight of the IPFPs in the control group, sham group, and US group were 0.32 ± 0.05 g, 0.32 ± 0.04 g (vs. control group, P = 0.895), and 0.38 ± 0.06 g (vs. control group, P = 0.017; vs. sham group, P = 0.033), respectively. The Osteoarthritis Research Society International (OARSI) scores of the IPFPs in the US group were 6.00 ± 1.91, which was higher than the scores of 2.50 ± 2.02 (P < 0.001) in the control group and of 2.75 ± 1.67 (P = 0.001) in the sham group.

CONCLUSIONS

The histopathological changes of the IPFPs as determined via MRI and microscopic structure appeared to occur much earlier than cartilage damage in PFOA. Furthermore, detecting and treating the IPFP changes may offer aid in the diagnosis and treatment of PFOA.

Worsening Knee Osteoarthritis Features on Magnetic Resonance Imaging 1 to 5 Years After Anterior Cruciate Ligament Reconstruction

BACKGROUND

An anterior cruciate ligament (ACL) injury is a well-established risk factor for the long-term development of radiographic osteoarthritis (OA). However, little is known about the early degenerative changes (ie, <5 years after injury) of individual joint features (ie, cartilage, bone marrow), which may be reversible and responsive to interventions.

PURPOSE

To describe early degenerative changes between 1 and 5 years after ACL reconstruction (ACLR) on magnetic resonance imaging (MRI) and explore participant characteristics associated with these changes.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Seventy-eight participants (48 men; median age, 32 years; median body mass index [BMI], 26 kg/m²) underwent 3.0-T MRI at 1 and 5 years after primary hamstring autograft ACLR. Early tibiofemoral and patellofemoral OA features were assessed with the MRI Osteoarthritis Knee Score. The primary outcome was worsening (ie, incident or progressive) cartilage defects, bone marrow lesions (BMLs), osteophytes, and meniscal lesions. Logistic regression with generalized estimating equations evaluated participant characteristics associated with worsening features.

RESULTS

Worsening of cartilage defects in any compartment occurred in 40 (51%) participants. Specifically, worsening in the patellofemoral and medial and lateral tibiofemoral compartments was present in 34 (44%), 8 (10%), and 10 (13%) participants, respectively. Worsening patellofemoral and medial and lateral tibiofemoral BMLs (14 [18%], 5 [6%], and 10 [13%], respectively) and osteophytes (7 [9%], 8 [10%], and 6 [8%], respectively) were less prevalent, while 17 (22%) displayed deteriorating meniscal lesions. Worsening of at least 1 MRI-detected OA feature, in either the patellofemoral or tibiofemoral compartment, occurred in 53 (68%) participants. Radiographic OA in any compartment was evident in 5 (6%) and 16 (21%) participants at 1 and 5 years, respectively. A high BMI (>25 kg/m²) was consistently associated with elevated odds (between 2- and 5-fold) of worsening patellofemoral and tibiofemoral OA features.

CONCLUSION

High rates of degenerative changes occur in the first 5 years after ACLR, particularly the development and progression of patellofemoral cartilage defects. Older patients with a higher BMI may be at particular risk and should be educated about this risk.

Relation of meniscus pathology to prevalence and worsening of patellofemoral joint osteoarthritis: the Multicenter Osteoarthritis Study

OBJECTIVE

To determine the relationship of meniscal damage to magnetic resonance imaging (MRI) features of compartment-specific patellofemoral joint (PFJ) osteoarthritis (OA) at baseline and 2 years later.

METHOD

Individuals from a prospective cohort of individuals aged 50-79 with or at risk of knee OA were included. At the 60-month and 84-month study visit, Whole-Organ MRI Score (WORMS) was used to assess meniscal tears and extrusions as well as cartilage damage and bone marrow lesions (BMLs) in the medial and lateral patella and trochlea. Worsening of structural features was defined as any increase in WORMS score from 60 to 84 months. Logistic regression was used to determine the cross-sectional and longitudinal relation of meniscus damage to features of compartment-specific PFJ OA.

RESULTS

Relative to knees without lateral meniscal pathology at baseline, those with grades 3-4 lateral meniscal tear and extrusion had greater risk of worsening of cartilage damage in the lateral PFJ 2 years later (Risk ratio: 1.7 [95% CI: 1.1-2.7) and (1.7 [1.2-2.5]), respectively. Relative to those without medial meniscal pathology at baseline, those with grades 1-2 (0.6 [0.4-0.9]) and 3-4 (0.7 [0.5-1.0]) medial meniscal tears had lower risk of worsening of BMLs in the medial PFJ 2 years later.

CONCLUSION

Meniscal tear and extrusion are associated with increased risk of medial and lateral PFJ OA and more severe meniscal pathology is associated with worsening of PFJ OA 2 years later. Lateral meniscal pathology appears to be more detrimental to the lateral PFJ.

Distal tibial tuberosity translation using TTA implants for the treatment of patella alta in large breed dogs

Introduction: Medial patellar luxation frequently occurs in dogs resulting in lameness with increasing incidence in large breed dogs. Patella alta has been defined as a patellar ligament length to patellar length ratio that is greater than two and may predispose to patellar luxation.

Objective: To describe the surgical technique for stabilization of the distal translation of the tibial tuberosity using tibial tuberosity advancement plates and the clinical outcomes with follow-up for clinical cases of dogs.

Methods: Dogs that were presented with the complaint of patellar luxation and that were concurrently diagnosed with patella alta and were greater than 20 kg in body weight underwent surgery using a tibial tuberosity advancement plate to stabilize the osteotomy. Radiographic assessment of A:PL distance (the ratio of the proximal aspect of the patella to the femoral condyle [A] to the patellar length [PL]), L:P ratio (ratio of the length of the patellar ligament to the diagonal length of the patella), and owner assessment were obtained.

Results: Eleven stifles in nine dogs underwent surgical correction with a mean preoperative L:P ratio of 2.47. There were no complications and the lameness resolved clinically. The mean A:PL ratios preoperatively (2.6 ± 0.22) and postoperatively (2.1 ± 0.25) were significantly different (p = 0.0003). All owners were satisfied with the outcome and all dogs had a resolution of lameness with no recurrence of patellar luxation.

Clinical significance: Stabilization of distal translation of the tibial tuberosity using tibial tuberosity advancement implants to correct patella alta in large breed dogs was feasible and resulted in good clinical outcome.

Patellofemoral morphology and alignment: reference values and dose-response patterns for the relation to MRI features of patellofemoral osteoarthritis

OBJECTIVE

We aimed to (1) determine reference values for trochlear morphology and patellofemoral (PF) alignment in adults without magnetic resonance imaging (MRI)-defined PF full thickness cartilage damage or knee pain; and (2) evaluate dose-response patterns for these measures with prevalent MRI-defined PF structural damage and/or knee pain.

DESIGN

The Framingham Community Cohort is a population-based sample of ambulatory adults aged ≥50 years. We evaluated six morphology and alignment measures using MRI (n = 985), and reported reference values (mean ± 2SD) in a subsample without MRI-defined PF full thickness cartilage damage or knee pain (n = 563). With restricted cubic spline Poisson regression, we evaluated dose-response patterns of each of the six measures with prevalent MRI-defined PF structural damage or joint pain. Our primary outcome was full thickness cartilage damage.

RESULTS

For dose-response curves, prevalence ratios (PR) increased monotonically for all measures except patellar tilt, which rose with both lateral and medial tilt. Associations were generally strongest in the lateral PF compartment. PR for the strongest predictors of full thickness cartilage damage reached clinical relevance (PR > 1.5) at sulcus angle (SA) ≥135.0°; patellar tilt angle at ≤1.0° and ≥15.0°; and bisect offset ≥57.0%. Lateral trochlear inclination (LTI) achieved PR > 1.5 at ≤23.0° for full thickness cartilage damage with pain.

CONCLUSIONS

SA, patellar tilt, and bisect offset were most strongly associated with full thickness cartilage damage. LTI, patellar tilt and bisect offset had stronger associations with the addition of pain. These findings contribute to better identifying a subset of patients who may benefit from mechanically based interventions.

Patellofemoral and tibiofemoral alignment in a fully weight-bearing upright MR: Implementation and repeatability

PURPOSE

To develop methods for evaluating 3D patellofemoral and tibiofemoral alignment in vertical open-bore magnetic resonance (MR) scanners, with participants upright and fully weight-bearing; and to evaluate the repeatability of these methods in individuals with patellofemoral osteoarthritis (OA) and in asymptomatic knees.

MATERIALS AND METHODS

Our methods extend previously validated, reliable methods for evaluating alignment into an upright MR environment. In 10 participants with early patellofemoral OA and 10 with asymptomatic knees, we acquired sagittal T₁ -weighted turbo spin echo images in a 3T scanner to create accurate participant-specific 3D anatomical surface models. In a vertical open-bore 0.5T MR scanner, we obtained lower-resolution sagittal gradient echo images to capture bony position and orientation data. Participants were scanned in a position of squatting with the knees flexed 30°, three separate times to evaluate repeatability. Bone segmentation was performed manually, surface models were registered to data from the 0.5T scanner, and 3D patellofemoral and tibiofemoral alignment was calculated in all six degrees of freedom (three rotations and three translations).

RESULTS

Intraclass correlation coefficients (ICCs) were ≥0.94, with the exception of patellar spin (0.79). Standard errors of measure (SEM) were <2° rotation and <0.9 mm translation. Repeatability remained adequate when stratified by group, with the exception of patellar spin (ICC 0.57 for asymptomatic knees vs. 0.91 for OA knees).

CONCLUSION

We demonstrate methods for evaluating 3D alignment in upright fully weight-bearing participant positions in a vertical open-bore MR scanner. With the exception of patellar spin, repeatability was good to excellent.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:841-847.

Clinical Significance of Medial Versus Lateral Compartment Patellofemoral Osteoarthritis: Cross-Sectional Analyses in an Adult Population With Knee Pain

OBJECTIVE

To determine the comparative prevalence, associations with selected patient characteristics, and clinical outcomes of medial and lateral compartment patellofemoral (PF) joint osteoarthritis (OA).

METHODS

Information was collected by questionnaires, clinical assessment, and radiographs from 745 eligible community-dwelling symptomatic adults age ≥50 years. PF joint space narrowing (JSN) and osteophytes were scored from skyline radiographs using the Osteoarthritis Research Society International atlas. Multilevel models were used to assess associations of compartmental PF joint OA with age, sex, body mass index (BMI) and varus-valgus malalignment, while median regression was used to examine associations with clinical outcomes (current pain intensity on a numeric rating scale [0-10] and the function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index [0-68]).

RESULTS

Isolated lateral PF joint OA was more common than isolated medial PF joint OA, particularly at higher severity thresholds. Irrespective of severity threshold, age (≥2 odds ratio [OR] 1.19 [95% confidence interval (95% CI) 1.12, 1.26]), BMI (≥2 OR 1.15 [95% CI 1.07, 1.24]), and valgus malalignment (≥2 OR 2.58 [95% CI 1.09, 6.07]) were associated with increased odds of isolated lateral JSN, but isolated medial JSN was only associated with age (≥2 OR 1.20 [95% CI 1.14, 1.27]). The pattern of association was less clear for PF joint osteophytes. Isolated lateral PF joint OA, defined by JSN or osteophytes, was associated with higher pain scores than isolated medial PF joint OA, but these differences were modest and were not significant. A similar pattern of association was seen for functional limitation but only when PF joint OA was defined by JSN.

CONCLUSION

Isolated lateral PF joint OA is more common than isolated medial PF joint OA, and it is more consistently associated with established OA risk factors. It is also associated with higher, but clinically nonsignificant, pain and function scores than isolated medial PF joint OA, particularly when PF joint OA is defined using JSN.

The Association of Forefoot Varus Deformity with Patellofemoral Cartilage Damage in Older Adult Cadavers

Forefoot alignment may contribute to patellofemoral joint (PFJ) osteoarthritis (OA) via its influence on the closed chain kinematics of the lower limb. The purpose of this cadaveric study was to investigate the relationship between forefoot varus and ipsilateral cartilage damage in the medial and lateral PFJ. Forefoot alignment measurements were obtained from the feet of 25 cadavers (n = 50). Cartilage damage in the medial and lateral PFJ of each knee was scored using the Outerbridge scale. The relative odds of medial and lateral PFJ cartilage damage in limbs with forefoot varus and valgus were determined using logistic regression. The relationship between increasing varus alignment and increasing odds of medial and lateral PFJ cartilage damage was assessed. Of the 51% of limbs with forefoot varus, 91.3% had medial, and 78.3% had lateral PFJ cartilage damage, compared with 54.6% and 68.2% of those with forefoot valgus. The former also had 3.0 times (95% CI 1.2, 7.7) the odds of medial PFJ damage; no association was found with lateral damage (OR 1.4, 95% CI 0.7, 3.0). Feet in the highest tertile of varus alignment had 3.9 times (95% CI 10, 15.3, P = 0.058) the odds of medial PFJ damage as those in the lowest tertile. The results of this study suggest a relationship between forefoot varus and medial PFJ cartilage damage in older adults. As forefoot varus may be modified with foot orthoses, these findings indicate a potential role for orthoses in the treatment of medial PFJ OA. Anat Rec, 300:1032-1038, 2017. © 2016 Wiley Periodicals, Inc.

Does Patella Tendon Tenodesis Improve Tibial Tubercle Distalization in Treating Patella Alta? A Computational Study

BACKGROUND

Patellofemoral malalignment associated with patella alta may cause pain and arthritis; because of this, the condition sometimes is treated surgically. Two common procedures are tibial tubercle distalization with or without patellar tendon tenodesis. However, the biomechanical consequences of these interventions for patella alta are not clearly understood.

QUESTIONS/PURPOSES

We evaluated changes in patellofemoral joint contact mechanics after tibial tubercle distalization and tibial tubercle distalization combined with patella tendon tenodesis. Specifically, we asked: (1) Are there biomechanical differences between these two types of procedures? (2) Is there an ideal range to distalize the patella?

METHODS

Subject-specific finite-element models were created for 10 individuals with patella alta (mean Insall-Salvati ratio of 1.34 ± 0.05). Input parameters for the finite-element models included subject-specific joint geometry, quadriceps muscle forces, and weightbearing patellofemoral joint kinematics. Virtual operations were conducted to simulate the two procedures. For distalization, the tibial tubercle and patella were displaced distally 4 mm to 20 mm in 4-mm increments based on the original model. At each level of distalization, the patella tendon was attached back to its original insertion to simulate the additional tenodesis procedure. Cartilage stress, contact area, and contact forces were quantified and compared between procedures and distalization levels.

RESULTS

Distalization and distalization + tenodesis reduced patellofemoral joint stress compared with the baseline of 1.02 ± 0.11 MPa. Distalization led to lower cartilage stress than distalization + tenodesis, and the effect size was relatively large (0.88 ± 0.10 MPa vs 0.92 ± 0.10 MPa; mean difference, 0.04 MPa [95% CI, 0.02 MPa-0.05 MPa], p < 0.01; effect size of 1.64 [Cohen's d], with Insall-Salvati ratio decreased to 0.95). For both procedures, the trend of stress reduction plateaued when the Install-Salvati ratio approached 0.95.

CONCLUSIONS

Cartilage stress appears lower using distalization as opposed to distalization + tenodesis in this finite-element analysis simulation. An Insall-Salvati ratio of 0.95 may be an ideal level for distalization; further distalization does not show additional benefits.

CLINICAL RELEVANCE

This study suggests that distalization may result in less stress than distalization + tenodesis, therefore future clinical research might be preferentially directed toward evaluating isolated distalization procedures.

Adolescent knee pain and patellar dislocations are associated with patellofemoral osteoarthritis in adulthood: A case control study

BACKGROUND

There is a lack of information about the association between patellofemoral osteoarthritis (PFOA) and both adolescent anterior knee pain (AKP) and previous patellar dislocations.

METHODS

This case-control study involved 222 participants from our knee arthroplasty database answering a questionnaire. One hundred and eleven patients suffering from PFOA were 1:1 matched by gender with a unicompartmental tibiofemoral arthritis control group. Multivariate correlation and binary logistic regression analysis were performed, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated.

RESULTS

An individual is 7.5 times more likely to develop PFOA if they have suffered from adolescent AKP (OR 7.5, 95% CIs 1.51 to 36.94). Additionally, experiencing a patellar dislocation increases the likelihood of development of PFOA, with an adjusted odds ratio of 3.2 (95% CIs 1.25 to 8.18). A 44-year difference in median age of first dislocation was also observed between the groups.

CONCLUSION

This should bring into question the traditional belief that adolescent anterior knee pain is a benign pathology. Patellar dislocation is also a significant risk factor. These patients merit investigation, we encourage clinical acknowledgement of the potential consequences when encountering patients suffering from anterior knee pain or patellar dislocation.

Clinical Impact of Coexisting Patellofemoral Osteoarthritis in Japanese Patients With Medial Knee Osteoarthritis

OBJECTIVE

To evaluate the clinical impact in knee osteoarthritis (OA) of coexisting patellofemoral (PF) joint OA (PFOA) in Japanese patients with medial tibiofemoral (TF) joint OA (TFOA).

METHODS

Patients with medial knee OA (n = 143) were enrolled. The radiographic severity of the TF and PF joints, anatomic axis angle of the TF joint, patellar alignment, trochlear morphology, patellar height, and passive range of motion (ROM) of the painful knee were evaluated. Additionally, the Japanese Knee Osteoarthritis Measure (JKOM) was used to investigate the association between the presence of PFOA and clinical symptoms.

RESULTS

PFOA was present in 98 of 143 patients (68.5%) with medial knee OA. Quantile regression analysis revealed that coexisting PFOA was associated with the pain-related subcategory of the JKOM. Furthermore, multiple logistic regression analysis showed that coexisting PFOA was associated with higher odds of reporting knee pain on using stairs while ascending (odds ratio [OR] 4.81 [95% confidence interval (95% CI) 1.73, 14.3]) and descending (OR 3.86 [95% CI 1.44, 10.8]). A more varus knee alignment and lower knee flexion ROM, which are features of patients with coexisting PFOA, were associated with knee pain while ascending/descending stairs. However, patellar alignment, trochlear morphology, and patellar height were not significantly associated with knee pain.

CONCLUSION

PFOA coexisting with medial knee OA was associated with worse clinical symptoms, particularly while ascending/descending stairs, although patellar alignment did not contribute to reporting knee pain. Further studies that include evaluation of the PF joint are warranted to develop a basis for an optimal intervention based on compartmental involvement.