Relationship of Trochlear Morphology and Patellofemoral Joint Alignment to Superolateral Hoffa Fat Pad Edema on MR Images in Individuals with or at Risk for Osteoarthritis of the Knee: The MOST Study

Association between quadriceps fat pad edema and patellofemoral osteoarthritis: a quantitative Q-Dixon-based magnetic resonance imaging (MRI) analysis

Background

Anterior knee pain (AKP) is a common symptom of patellofemoral osteoarthritis (PFOA). There is limited prospective evidence supporting the relationships between patellofemoral maltracking parameters, AKP, and PFOA. Thus, this prospective cross-sectional study aimed to determine the association between quadriceps fat pad (QFP) edema and patellofemoral maltracking in patients with chronic AKP and to evaluate the feasibility and diagnostic performance of a PFOA assessment using fat fraction (FF) and T2* based on Q-Dixon.

Methods

This was a cross-sectional study with prospective data collection. Patients with chronic AKP were recruited from an orthopedic outpatient magnetic resonance imaging (MRI) waiting room at Shanghai Tongren Hospital between November 1, 2022, and April, 30, 2023. Exclusion criteria included age of <18 years, knee trauma, major internal derangement, prior surgery/arthroscopy, pre-existing joint diseases, and contraindications to MRI. MRI was performed using a 3.0-T instrument, and patellofemoral maltracking parameters were measured. Patellofemoral feature-relevant items, including patellar cartilage defects, patellar bone marrow lesions (BMLs), patellar osteophytes, anterior femoral osteophytes, Hoffa synovitis, and synovitis-effusion, from the semi-quantitative MRI Osteoarthritis Knee Score (MOAKS) were measured. The Anterior Knee Pain Scale (AKPS) was used to assess pain and function. FF/T2* measurement differences between groups and their associations with maltracking metrics, osteoarthritis grading based on the Iwano grading system, MOAKS, and AKPS, were investigated. Based on Iwano grading, the participants were categorized as having no-PFOA (n=40), mild PFOA (n=40), and advanced PFOA (n=40). Chi-squared and one-way analysis of variance were used to assess potential differences between the groups. Spearman's correlation test was used to analyze the correlation between the morphological parameters, AKPS, Iwano grade, MOAKS, and MRI quantitative values. Receiver operating characteristic (ROC) curves assessed the area under the curve (AUC), sensitivity, and specificity of quantitative values for distinguishing PFOA from no-PFOA.

Results

Among the 120 included patients, those in the mild (86.2±8.5) and advanced (83.9±9.5) PFOA groups had significantly lower AKPS scores than those in the no-PFOA group (88.8±7.3) (P=0.03). The mean FF and T2* values of the QFP were significantly higher in the no-PFOA group than those in the mild and advanced PFOA groups (P<0.001 for FF and P=0.02 for T2*). Quantitative data on the QFP and patellofemoral maltracking parameters showed no association. FF (r=-0.686, P<0.001) and T2* (r=-0.314, P=0.008) showed a negative correlation with the Iwano grade. The AUCs for PFOA diagnosis were 0.906 [95% confidence interval (CI), 0.853-0.960] (FF) and 0.744 (95% CI, 0.657-0.831) (T2*).

Conclusions

QFP FF and T2* were not associated with patellofemoral maltracking parameters but with increased PFOA in patients with AKP, suggesting that QFP abnormalities play a role in PFOA. Therefore, a quantitative QFP assessment (FF and T2*) based on Q-Dixon technology could be a convenient and reliable new imaging biomarker for PFOA severity during clinical diagnosis, treatment, and follow-up.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Superolateral Hoffa fat pad edema in adolescent competitive alpine skiers: temporal evolution over 4 years and risk factors

OBJECTIVES

To longitudinally assess and correlate the prevalence of superolateral Hoffa fat pad (SHFP) edema with changes in features of the knee extensor mechanism in adolescent competitive alpine skiers over 48 months.

METHODS

Competitive alpine skiers were prospectively enrolled in 2018 and underwent bilateral knee MRI at baseline and after 48 months. MRI was assessed for the prevalence of SHFP edema. Features of the knee extensor mechanism were assessed by measuring the trochlear sulcus angle and depth, lateral and medial trochlear inclination, trochlear angle, patella tilt, Insall‒Salvati ratio (ISR), and patellar ligament to lateral trochlear facet (PL-T) distance. Separate logistic regression models were used to calculate the odds ratios between each measurement and the presence of SHFP edema at both time points.

RESULTS

Sixty-three athletes were included in the study (mean age 15.3 ± 1.3 years, 25 women). At baseline, 23 knees had SHFP edema, increasing to 34 knees at the 48-month follow-up. At baseline, knees with measurements in the highest quartile for ISR and lowest quartile for trochlear depth and PL-T were 9.3, 5.1, and 7.7 times more likely to show SHFP edema, respectively. At follow-up, these correlations were confirmed and additionally, knees with measurements in the highest quartile for trochlear sulcus angle and the lowest quartile for lateral trochlear inclination were 4.1 and 3.4 times more likely to show SHFP edema.

CONCLUSION

An increased prevalence of SHFP edema in competitive alpine skiers during adolescence was associated with persistent high-riding patella, reduced patellar ligament to trochlear distance, and flattened lateral trochlear facet.

CRITICAL RELEVANCE STATEMENT

In clinical routine, assessment of the mechanical properties of the knee extensor mechanism, together with anatomical developments during adolescence, may improve the understanding and management of patellofemoral instability.

KEY POINTS

• Superolateral Hoffa fat pad (SHFP) edema is a frequent cause of anterolateral knee pain but the role of predisposing factors is still debated. • A higher prevalence of SHFP edema was associated with high-riding patella, reduced patellar ligament to trochlear distance, and flattened lateral trochlear facet. • Understanding of the mechanical interaction and the anatomical development of the knee during adolescence provides further insight into the development of SHFP edema.

Association among peripatellar fat pad edema and related patellofemoral maltracking parameters: a case-control magnetic resonance imaging study

BACKGROUND

The peripatellar fat pads are critical for protective cushioning during movement, and their endocrine function has been shown to affect osteoarthritis. Magnetic resonance imaging (MRI) is frequently used to visualize edema of the peripatellar fat pads due to injury. In this study, we aimed to assess the relationship between peripatellar fat pad edema and patellofemoral maltracking MRI parameters and investigate the association among cases of peripatellar fat pad edema.

METHODS

Age- and sex-matched peripatellar fat pad edema cases were identified and divided into superolateral Hoffa, quadriceps, and prefemoral groups. Images were assessed according to tibial tuberosity lateralization, trochlear dysplasia, patellar alta, patellar tilt, and bisect offset. McNemar's test or paired t-tests and Spearman's correlation were used for statistical analysis. Interobserver agreement was assessed with the intraclass correlation coefficient.

RESULTS

Of 1210 MRI scans, 50, 68, and 42 cases were in the superolateral Hoffa, quadriceps, and prefemoral groups, respectively. Subjects with superolateral Hoffa fat pad edema had a lower lateral trochlear inclination (p = 0.028), higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.021) ratios, and lower patellotrochlear index (p < 0.001) than controls. The prefemoral group had a lower lateral trochlear inclination (p = 0.014) and higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.004) ratios compared with the control group. In contrast, the patellotrochlear index (p = 0.001) was lower. Mean patellar tilt angle (p = 0.019) and mean bisect offset (p = 0.005) were significantly different between cases and controls. The quadriceps group showed no association. Superolateral Hoffa was positively correlated with prefemoral (p < 0.001, r = 0.408) and negatively correlated with quadriceps (p < 0.001, r = -0.500) fat pad edema.

CONCLUSIONS

Superolateral Hoffa and prefemoral fat pad edemas were associated with patellar maltracking parameters. Quadriceps fat pad edema and maltracking parameters were not associated. Superolateral Hoffa fat pad edema was positively correlated with prefemoral and negatively correlated with quadriceps fat pad edema.

Using Dual-Orthogonal Fluoroscopy and CT to Assess the Relationship Between Knee Morphology and Patellar Kinematics in Patients With Patellofemoral Pain

INTRODUCTION

Patellofemoral pain (PFP) is one of the most common knee overuse injuries, with studies suggesting PFP as a precursor for early knee osteoarthritis. The etiology of PFP is multi-factorial; however, patellar mal-tracking has been regarded as a primary mechanism. Details of this multi-factorial mechanism have been unclear because of the limitations in evaluating in-vivo, three-dimensional (3D) patellofemoral joint movement during dynamic activities accurately. Alternatively, studies have demonstrated the high accuracy and repeatability of dual fluoroscopy and CT/MRI for measuring knee joint motion.

OBJECTIVE

This study uses dual fluoroscopy and CT to investigate the associations between joint morphology and patellar kinematics in healthy controls and subjects with PFP.

METHODS

Eight PFP females (29.7±10.6 years) and 10 healthy females (25.0±7.7 years) were recruited and screened by a sports medicine physician. CT imaging was performed on participants in a supine with the knee extended, and ankle and hip in neutral alignment. Dual-orthogonal fluoroscopy measured patellar movement while participants performed a lunge task. A calibration algorithm was used to register the 3D CT model to 2D fluoroscopy image to calculate the relative position and angles of the patella based on the clinical definition of patellar motion. Measures of patellar and trochlear morphology were generated and correlated to kinematic data.

RESULTS AND CONCLUSION

There was a significant difference in the patellar-to-trochlear width ratio; however, no other significant differences in CT morphology measurements were present between groups. For PFP patients in the weight-bearing extended position, there was a moderate positive correlation between the patellar-to-trochlear width ratio and medial-lateral patellar shift (τ = 0.643, p = 0.026). Healthy controls in this position demonstrated a moderate positive correlation between the lateral-trochlear inclination angle and medial-lateral patellar shift (τ = 0.600, p = 0.016) and moderate negative correlation between medial trochlear inclination angle and medial-lateral patellar shift (τ = -0.511, p = 0.040). The findings suggest that, for this cohort, there is correlation between morphology and patellar kinematics. Passive and active stabilizers likely have a role in mal-tracking.

Predisposing factors for Hoffa's fat pad syndrome: a systematic review

BACKGROUND

Hoffa's fat pad syndrome has been defined as impingement of Hoffa's fat pad, leading to oedema and fibrosis. The primary aim of this systematic review was to identify morphological differences in Hoffa's fat pad between patients with and without Hoffa's fat pad syndrome, evaluating them as risk factors predisposing to its development. The secondary aim was to summarize and evaluate current evidence pertaining to the management of Hoffa's fat pad syndrome.

MATERIALS AND METHODS

The protocol for this review was prospectively registered (PROSPERO registration: CRD42022357036). Electronic databases, currently registered studies, conference proceedings and the reference lists of included studies were searched. All studies evaluating differences in Hoffa's fat pad anatomy under imaging between patients with and without Hoffa's fat pad syndrome were included, as well as those exploring epidemiological factors predisposing to its development (ethnicity, employment status, sex, age and BMI), and studies reporting on the effect of treatment on Hoffa's fat pad morphology.

RESULTS

A total of 3871 records were screened. Twenty one articles satisfied the inclusion criteria, evaluating 3603 knees of 3518 patients. Patella alta, increased tibial tubercle-tibial groove distance, and increased trochlear angle were found to predispose the development of Hoffa's fat pad syndrome. Trochlear inclination, sulcus angle, patient age and BMI were not associated with this condition. The link between Hoffa's fat pad syndrome and ethnicity, employment, patellar alignment, Hoffa's fat pad composition, physical activity and other pathological processes cannot be established due to lack of evidence. No studies reporting on treatment for Hoffa's fat pad syndrome were identified. Though weight loss and gene therapy may provide symptomatic relief, further research is required to corroborate these claims.

CONCLUSION

Current evidence suggests that high patellar height, TT-TG distance, and trochlear angle predispose the development of Hoffa's fat pad syndrome. In addition, trochlear inclination, sulcus angle, patient age and BMI do not seem to be associated with this condition. Further research should explore the link between Hoffa's fat pad syndrome and sport as well as other conditions pertaining to the knee. In addition, further study evaluating treatment approaches for Hoffa's fat pad syndrome is required.

Overuse-Related Injuries of the Knee

Overuse-related injuries of the knee joint and periarticular soft tissues include a heterogenous group of sports and nonsports-related injuries. These conditions include friction and impingement syndromes, bone stress injuries, bursitis, and tendon-related pathology such as tendinopathy and snapping. Traction apophysitis are also discussed as commonly seen in the pediatric population. Although multiple imaging modalities can be used, this review focuses on MR imaging, which is the most common and, often, the only modality used.

Effects of hindlimb suspension on development of proximal and distal femur morphological abnormalities in growing rats

Although morphological abnormalities of the femur are known predisposing factors for numerous musculoskeletal disorders, the etiology of these abnormalities is poorly understood. This study aimed to investigate whether femoral morphogenesis is affected by hindlimb suspension (HS) in growing rats. We used 41 four-week-old female rats in this study. In the HS groups, rats were suspended from their tails for 2, 4, and 8 weeks. Age-matched animals were used as controls. We examined morphological indices of the femur using three-dimensional reconstructed images from X-ray computed tomography. The femoral neck anteversion angle (AVA) was higher with growth in the experimental groups and did not differ in control groups. The AVAs in the HS groups were larger than controls at any time point. In the control groups, the trochlear angle (TA) was higher, rotating inward with growth, but did not differ in the HS groups. The TAs in the HS groups were smaller and rotated more outward compared with the control groups at any time point. The height ratios of the medial and lateral condyles (MC/LC), an asymmetry index, were larger in the HS groups compared to controls at any time point. There were strong relationships between proximal (AVA) and distal morphologies, such as the TA (Spearman's coefficient [r_s ] = -0.80, p < 0.001) and MC/LC (r_s  = 0.79, p < 0.001). Our data suggest that sufficient physical activity in early life may protect against morphological femur abnormalities associated with hip and knee joint diseases.

Magnetic Resonance Imaging-Defined Osteoarthritis Features and Anterior Knee Pain in Individuals With, or at Risk for, Knee Osteoarthritis: A Multicenter Study on Osteoarthritis

OBJECTIVE

The lack of strong association between knee osteoarthritis (OA) structural features and pain continues to perplex researchers and clinicians. Evaluating the patellofemoral joint in addition to the tibiofemoral joint alone has contributed to explaining this structure-pain discordance, hence justifying a more comprehensive evaluation of whole-knee OA and pain. The present study, therefore, was undertaken to evaluate the association between patellofemoral and tibiofemoral OA features with localized anterior knee pain (AKP) using 2 study designs.

METHODS

Using cross-sectional data from the Multicenter Osteoarthritis Study, our first approach was a within-person, knee-matched design in which we identified participants with unilateral AKP. We then assessed magnetic resonance imaging (MRI)-derived OA features (cartilage damage, bone marrow lesions [BMLs], osteophytes, and inflammation) in both knees and evaluated the association of patellofemoral and tibiofemoral OA features to unilateral AKP. In our second approach, MRIs from 1 knee per person were scored, and we evaluated the association of OA features to AKP in participants with AKP and participants with no frequent knee pain.

RESULTS

Using the first approach (n = 71, 66% women, mean ± SD age 69 ± 8 years), lateral patellofemoral osteophytes (odds ratio [OR] 5.0 [95% confidence interval (95% CI) 1.7-14.6]), whole-knee joint effusion-synovitis (OR 4.7 [95% CI 1.3-16.2]), and infrapatellar synovitis (OR 2.8 [95% CI 1.0-7.8]) were associated with AKP. Using the second approach (n = 882, 59% women, mean ± SD age 69 ± 7 years), lateral and medial patellofemoral cartilage damage (prevalence ratio [PR] 2.3 [95% CI 1.3-4.0] and PR 1.9 [95% CI 1.1-3.3], respectively) and lateral patellofemoral BMLs (PR 2.6 [95% CI 1.5-4.7]) were associated with AKP.

CONCLUSION

Patellofemoral but not tibiofemoral joint OA features and inflammation were associated with AKP.

Effect of Korean Medicine Treatments for Fat Pad Syndrome of Knee Joint: A Case Report

Fat pad syndrome is a knee joint condition/disease where acute or chronic inflammation occurs in the fat pad of the knee joint, and it is a cause of anterior knee pain. Fat pad syndrome usually occurs concurrently with other conditions/diseases to collectively cause anterior knee pain. No study to date has reported the treatment of anterior knee pain solely due to fat pad syndrome. Here, we report a case of fat pad syndrome of the knee joint as the sole cause of anterior knee pain in a 49-year-old woman who received integrated Korean medicine treatments (pharmacopuncture, acupuncture, herbal medicine, deep fascial meridian therapy, and chuna). Using patient-reported pain scale scores, the level of the patient’s pain was relieved, and her mobility improved. Integrated Korean medicine treatments could be effective for patients who have fat pad syndrome of the knee joint.

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.

A quantitative MRI investigation of the association between iliotibial band syndrome and patellofemoral malalignment

Background

The iliotibial band (ITB) has a wide patellar insertion that provides lateral restraint to the patella and maintains the patellofemoral joint's stability. There has been limited investigation into the relationship between patellofemoral malalignment and iliotibial band syndrome (ITBS).

Methods

We retrospectively analyzed 47 knees with ITBS by retrieving magnetic resonance imaging (MRI) data collected over an approximately 6-year period from our database. The Insall-Salvati ratio, lateral patellofemoral angle (LPA), lateral patellar tilt (LPT), lateral trochlear length (LTL), angle of the non-weight-bearing facet of the lateral femoral condyle (nwb-LFCA), and the ITB-lateral femoral condyle (IT-LFC) distance were measured on MR images. The knees of 47 age- and gender-matched subjects were enrolled as the normal group.

Results

In the ITBS group, over one third (34%, 16/47) of knees had abnormal patellofemoral measurements, including 8 (17%, 8/47) knees with patellar alta, 11 (23.4%, 11/47) knees with an abnormally decreased LPA, and 5 (10.6%, 5/47) knees with an abnormally increased LPT indicating lateral patellar tilt. Moreover, 8 knees had simultaneous combinations of two or three abnormality parameters, and 8 (17%, 8/47) knees presented with superolateral Hoffa's fat pad edema. The Insall-Salvati ratio, LPT, and nwb-LFCA in the ITBS group were significantly higher than those in the normal group (P=0.001, P<0.001, and P<0.001, respectively); the LPA and IT-LFC distances in the ITBS group were significantly lower (P=0.003, P<0.001, respectively) than those in the normal group. There were mild to moderate correlations between the MRI parameters and ITBS (P=0.006, P<0.001, respectively).

Conclusions

This study confirmed that a higher position or lateral tilt of the patella and a steeper morphology of the anterior part of the lateral femoral condyle were associated with the development of ITBS, which is helpful in understanding and further exploring the mechanism of ITBS.

The relationship between patellar tilt and quadriceps patellar tendon angle with anatomical variations and pathologies of the knee joint

PURPOSE

To investigate the association between the knee joint anatomical variations and pathologies, and to describe the quadriceps patellar tendon angle (QPA).

METHODS

MRIs of 406 cases with a lateral patellar tilt angle (LPT)>5° and a control group of 40 cases with an LPT<5° were retrospectively evaluated. QPA, LPT, trochlear sulcus angle (TSA), tibial tubercle-trochlear groove distance (TT-TG), Insall-Salvati index (ISI), patellar tendon length (PTL), patellar height (PH), lateral trochlear inclination (LTI), trochlear facet asymmetry ratio (TFA) and trochlear depth (TD) were measured. Presence of fat-pad oedema, patellar and trochlear chondromalacia, patellar and quadriceps tendinosis and effusion were evaluated.

RESULTS

The medians of TSA, PTL, ISI and TT-TG were significantly higher; LTI, TFA and TD were significantly lower in the patient group. The prevalence of SL-Hoffa, non-SL-Hoffa, suprapatellar and prefemoral fat-pad oedema, effusion and chondromalacia were significantly higher in the patient group. LPT was found to be positively correlated with TSA and TT-TG, and negatively correlated with LTI and TD. Cases with trochlear dysplasia, patellar chondromalacia and quadriceps tendinosis had significantly higher LPT. There was a positive correlation between QPA and TSA and a negative correlation between QPA and LTI. Cases with trochlear dysplasia, non-SL-Hoffa oedema, prefemoral fat-pad oedema and quadriceps tendinosis had significantly higher QPA. We found 10°<LPT to be a cut-off value to cause SL-Hoffa fat pad oedema.

CONCLUSION

The anatomical variations of the knee joint are associated with fat-pad, cartilage and tendon pathologies.

Longitudinal analysis of the contribution of 3D patella and trochlear bone shape on patellofemoral joint osteoarthritic features

To explore bone shape features that are associated with patellofemoral joint (PFJ) osteoarthritic features. Thirty subjects with PFJ degeneration (six males, 53.2 ± 9.8 years) and 23 controls (12 males, 48.1 ± 10.6 years) were included. Magnetic resonance (MR) assessment was performed to provide bone segmentation, morpholgocial grading, and cartilage relaxation times. In addition, subject self-reported symptoms were reported. Logistic regressions were used to identify the shape features that were associated with the presence and worsening of PFJ morphological lesions over 3 years, and worsening of self-reported symptoms. Statistical parametric mapping was used to evaluate the associations between shape features and cartilage relaxation times at 3 years. Results indicated that subjects with PFJ degeneration exhibited a trochlea with longer lateral condyle and shallower trochlear groove (adjusted odds ratio [OR] = 0.30; 95% confidence interval [CI]: 0.10, 0.86; P = .025). Subjects with worsening of PFJ degeneration exhibited a patella with equally distributed facets (adjusted OR = 3.14; 95% CI: 1.05, 9.37; P = .040) and lateral bump (adjusted OR = 0.14; 95% CI: 0.02, 0.83; P = .030). No shape features were associated with worsening of self-reported symptoms. Elevated T_1ρ and T₂ times at 3 years were associated with a patella with a lateral hook, equally distributed facets, round and thick as well as a trochlea larger in size (R = 0.38~0.46, P = .015~.025). The study demonstrated the ability of 3D statistical shape modeling to quantify patella and trochlear bone shape features that are associated with the presence and progression of PFJ osteoarthritic features.

Osteoarthritic knees have a highly variable patellofemoral alignment: a systematic review

PURPOSE

This systematic review aimed to evaluate the variability of patellofemoral (PF) alignment and trochlear morphology in osteoarthritic knees.

METHODS

PF alignment of the knee was defined by the following parameters: the sulcus angle (SA), femoral trochlear depth (FTD), patellar tilt angle (PTA), lateral patellofemoral angle (LPFA), lateral femoral trochlear inclination (LFTI) and tibial tubercle-trochlear groove distance (TT-TG). The electronic databases MEDLINE and EMBASE were searched from database inception to the search date (February 19, 2019) and were screened for relevant studies. The PRISMA guidelines were followed. Articles reporting PF alignment measurements of osteoarthritic knees in patients over 40 years old were included. Data were extracted and methodological quality was assessed using a 14-item checklist.

RESULTS

A total of 8 studies met the inclusion criteria. The studies reported mean values ± SD between 120° and 141.1° ± 7.7 for the SA; 5.8 mm ± 1.4 for the FTD; between - 0.1° ± 3.3 and 10.3° ± 5.7 for the PTA; between 5.8° ± 5.4 and 17° for the LPFA; between 23.2° ± 5.0 and 27.1° ± 4.4 for the LFTI; and 5.8 mm ± 5.4 for the TT-TG.

CONCLUSION

PF alignment in the osteoarthritic knee is more variable than expected. This finding should encourage surgeons to consider the individual preoperative PF alignment more precisely with the aim of reducing anterior knee pain (AKP) after TKA. 3D-CT imaging might be of great value to analyse the PF alignment in an appropriate way.

LEVEL OF EVIDENCE

Level III.

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.

Superolateral Hoffa Fat Pad Edema and Patellofemoral Maltracking: Systematic Review and Meta-Analysis

OBJECTIVE. The purpose of this study is to clarify which imaging parameters of patellofemoral maltracking are associated with superolateral Hoffa fat pad (SHFP) edema. MATERIALS AND METHODS. A systematic search of the MEDLINE, Embase, and Cochrane Library databases was performed to identify studies evaluating the relationship between SHFP edema and patellofemoral maltracking. Parameters for assessing patellofemoral maltracking on MRI were reviewed for each study. Two reviewers performed study selection, methodologic quality assessment, and data extraction. RESULTS. Nine studies were eligible for inclusion in the present study. From the included studies, nine parameters assessing patellofemoral maltracking were analyzed: lateral patellofemoral angle, patellar tilt, patellar lateralization, trochlear depth, sulcus depth, sulcus angle, lateral trochlear inclination, distance between the tibial tuberosity and trochlear groove, and the Insall-Salvati ratio. Patients with SHFP edema had greater patellar tilt (standardized mean difference, 0.89°; 95% CI, 0.38-1.40°; p = 0.0006), greater patellar lateralization (standardized mean difference, 0.78 mm; 95% CI, 0.21-1.36 mm; p = 0.008), greater distance between the tibial tuberosity and trochlear groove (standardized mean difference, 0.96 mm; 95% CI, 0.48-1.44 mm; p < 0.0001), and higher Insall-Salvati ratio (standardized mean difference, 1.94; 95% CI, 1.29-2.60; p < 0.00001) than patients without SHFP edema. CONCLUSION. Patellofemoral maltracking imaging parameters, such as a more laterally displaced patella, greater TTTG distance, and patella alta, are correlated with SHFP edema.

Magnetic resonance imaging of impingement and friction syndromes around the knee

The knee is a complex joint with its function dependent on a combination of osseous and soft tissue structures. Alteration in the relationship of these tissues, due to either acute or chronic repetitive injury with possible underlying congenital predisposing factors, can result in impingement between the structures resulting in pain, particularly on activity. The purpose of this article is to provide a comprehensive review of the MRI features of various impingement syndromes around the knee.

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.

Quantitative Signal Intensity Alteration in Infrapatellar Fat Pad Predicts Incident Radiographic Osteoarthritis: The Osteoarthritis Initiative

OBJECTIVE

To determine whether infrapatellar fat pad (IPFP) signal intensity measures are predictive of incident radiographic osteoarthritis (ROA) over 4 years in the Osteoarthritis Initiative study.

METHODS

Case knees (n = 355), as defined by incident ROA, were matched 1:1 with control knees, according to sex, age, and radiographic status. T2-weighted magnetic resonance images were assessed at P0 (the visit when incident ROA was observed on a radiograph), P1 (1 year prior to P0), and baseline and used to assess IPFP signal intensity semiautomatically. Conditional logistic regression analyses were performed to assess the risk of incident ROA associated with IPFP signal intensity alteration, after adjustment for covariates.

RESULTS

The mean age of the participants was 60.2 years, and most (66.7%) were female and overweight (mean body mass index 28.3 kg/m² ). Baseline IPFP measures including the mean value and standard deviation of IPFP signal intensity, the mean value and standard deviation of IPFP high signal intensity, median and upper quartile values of IPFP high signal intensity, and the clustering effect of high signal intensity were associated with incident knee ROA over 4 years. All P1 IPFP measures were associated with incident ROA after 12 months. All P0 IPFP signal intensity measures were associated with ROA.

CONCLUSION

The quantitative segmentation of high signal intensity in the IPFP observed in our study confirms the findings of previous work based on semiquantitative assessment, suggesting the predictive validity of semiquantitative assessment of IPFP high signal intensity. The IPFP high signal intensity alteration could be an important imaging biomarker to predict the occurrence of ROA.

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.

Osteoarthritis year in review 2018: imaging

PURPOSE

To provide a narrative review of the most relevant original research published in 2017/2018 on osteoarthritis imaging.

METHODS

The PubMed database was used to recover all relevant articles pertaining to osteoarthritis and medical imaging published between 1 April 2017 and 31 March 2018. Review articles, case studies and in vitro or animal studies were excluded. The original publications were subjectively sorted based on relevance, novelty and impact.

RESULTS AND CONCLUSIONS

The publication search yielded 1,155 references. In the assessed publications, the most common imaging modalities were radiography (N = 708) and magnetic resonance imaging (MRI) (355), followed by computed tomography (CT) (220), ultrasound (85) and nuclear medicine (17). An overview of the most important publications to the osteoarthritis (OA) research community is presented in this narrative review. Imaging studies play an increasingly important role in OA research, and have helped us to understand better the pathophysiology of OA. Radiography and MRI continue to be the most applied imaging modalities, while quantitative MRI methods and texture analysis are becoming more popular. The value of ultrasound in OA research has been demonstrated. Several multi-modality predictive models have been developed. Deep learning has potential for more automatic and standardized analyses in future OA imaging research.

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.

Superolateral Hoffa's fat pad (SHFP) oedema and patellar cartilage volume loss: quantitative analysis using longitudinal data from the Foundation for the National Institute of Health (FNIH) Osteoarthritis Biomarkers Consortium

OBJECTIVES

To determine the association of superolateral Hoffa's fat pad (SHFP) oedema and patellofemoral joint structural damage in participants of Foundation for the National Institute of Health Osteoarthritis Biomarkers Consortium study.

METHODS

Baseline and 24-month MRIs of 600 subjects were assessed. The presence of SHFP oedema (using 0-3 grading scale) and patellar morphology metrics were determined using baseline MRI. Quantitative patellar cartilage volume and semi-quantitative MRI osteoarthritis knee score (MOAKS) variables were extracted. The associations between SHFP oedema and patellar cartilage damage, bone marrow lesion (BML), osteophyte and morphology were evaluated in cross-sectional model. In longitudinal analysis, the associations between oedema and cartilage volume loss (defined using reliable change index) and MOAKS worsening were evaluated.

RESULTS

In cross-sectional evaluations, the presence of SHFP oedema was associated with simultaneous lateral patellar cartilage/BML defects and inferior-medial patellar osteophyte size. A significant positive correlation between the degree of patella alta and SHFP oedema was detected (r = 0.259, p < 0.001). The presence of oedema was associated with 24-month cartilage volume loss (odds ratio (OR) 2.11, 95% confidence interval 1.46-3.06) and medial patellar BML size (OR 1.92 (1.15-3.21)) and number (OR 2.50 (1.29-4.88)) worsening. The optimal cut-off value for the grade of baseline SHFP oedema regarding both presence and worsening of patellar structural damage was ≥ 1 (presence of any SHFP hyperintensity).

CONCLUSIONS

The presence of SHFP oedema could be considered as a predictor of future patellar cartilage loss and BML worsening, and an indicator of simultaneous cartilage, BML and osteophyte defects.

KEY POINTS

• SHFP oedema was associated with simultaneous lateral patellar OA-related structural damage. • SHFP oedema was associated with longitudinal patellar cartilage loss over 24 months. • SHFP oedema could be considered as indicator and predictor of patellar OA.

Is superolateral Hoffa's fat pad hyperintensity a marker of local patellofemoral joint disease? - The MOST study

PURPOSE

To determine the relation of superolateral Hoffa's fat pad (SHFP) hyperintensity to cartilage damage and bone marrow lesions (BMLs) in the patellofemoral joint (PFJ) and tibiofemoral joint (TFJ).

METHODS

We used data from the 60 and 84-month study visits from the Multicenter Osteoarthritis (MOST) study. SHFP hyperintensity and Hoffa-synovitis were graded from 0 to 3. Cartilage damage and BMLs were scored in the PFJ and TFJ. Structural damage was defined as: any cartilage damage, full-thickness cartilage damage and any BML. Worsening structural damage was defined as any increase in cartilage and BML scores. Logistic regression was used to determine the relation of SHFP hyperintensity and Hoffa-synovitis (>0) to structural damage, adjusting for age, sex and body mass index (BMI).

RESULTS

1,094 knees were included in the study. Compared to knees without SHFP hyperintensity, those with SHFP hyperintensity had 1.2 (95% Confidence Interval (CI), 1.1-1.4), 1.7 (1.3-2.3) and 1.6 (1.3-1.9) times the prevalence of any cartilage damage, full-thickness cartilage damage, and BMLs in the lateral PFJ respectively, and 1.1 (1.0-1.2), 1.3 (1.0-1.8), and 1.2 (1.0-1.4) times the prevalence of any cartilage damage, full-thickness cartilage damage, and BMLs in the medial PFJ. SHFP hyperintensity was associated with worsening BMLs in the medial PFJ (RR: 1.4 (1.0-1.9)). In general, there was no relation between SHFP hyperintensity and TFJ outcomes. Hoffa-synovitis was associated both cross-sectionally and longitudinally with structural damage, regardless of definition, in all compartments.

CONCLUSION

SHFP hyperintensity may be a local marker of PFJ structural damage.