The effect of bracing on patellofemoral joint stress during free and fast walking

Women with patellofemoral pain show changes in trunk and lower limb sagittal movements during single-leg squat and step-down tasks

BACKGROUND

Changes in the trunk and lower limbs' sagittal movements may cause patellofemoral pain (PFP) because they influence the forces acting on this joint.

OBJECTIVES

To compare trunk and lower limb sagittal kinematics between women with and without PFP during functional tests and to verify whether sagittal trunk kinematics are correlated with those of the knees and ankles.

METHODS

A total of 30 women with PFP and 30 asymptomatic women performed single-leg squat (SLS) and step-down (SD) tests and were filmed by a camera in the sagittal plane. The trunk inclination angle, forward knee displacement, and ankle angle were calculated.

RESULTS

The PFP group exhibited less trunk flexion (SLS, p = .006; SD, p = .016) and greater forward knee displacement (SLS, p = .001; SD, p = .004) than the asymptomatic group; there was no significant difference in ankle angle (SLS, p = .074; SD, p = .278). Correlation analysis revealed that decreased trunk flexion was associated with increased forward knee displacement (SLS, r = -0.439, p = .000; SD, r = -0.365, p = .004) and ankle dorsiflexion (SLS, r = -0.339, p = .008; SD, r = -0.356, p = .005).

CONCLUSION

Women with PFP present kinematic alterations of the trunk and knee in the sagittal plane during unipodal activities. Furthermore, the trunk and lower limb sagittal movements were interdependent.

The effects of a sleeve knee brace during stair negotiation in patients with symptomatic patellofemoral osteoarthritis

BACKGROUND

The patellofemoral joint is an important source of pain in knee osteoarthritis. Most biomechanical research in knee osteoarthritis has focused on the tibiofemoral joint during level walking. It is unknown what happens during stair negotiation in patients with patellofemoral joint osteoarthritis, a task commonly increasing pain. Conservative therapy for patellofemoral joint osteoarthritis includes the use of a sleeve knee brace. We aimed to examine the effect of a sleeve knee brace on knee biomechanics during stair negotiation in patellofemoral joint osteoarthritis patients.

METHODS

30 patellofemoral joint osteoarthritis patients (40-70 years) ascended and descended an instrumented staircase with force plates under two conditions - wearing a Lycra flexible knee support (Bioskin Patellar Tracking Q Brace) and no brace (control condition). Knee joint kinematics (VICON) and kinetics were recorded.

FINDINGS

During stair ascent, at the knee, the brace significantly reduced the maximal flexion angle (2.70, P = 0.002), maximal adduction angle (2.00, P = 0.044), total sagittal range of motion (2.00, P = 0.008), total frontal range of motion (1.70, P = 0.023) and sagittal peak extension moment (0.05 Nm/kg, P = 0.043) compared to control. During stair descent, at the knee, the brace significantly reduced the maximal flexion angle (1.80, P = 0.039) and total sagittal range of motion (1.50, P = 0.045) compared to control.

INTERPRETATION

The small changes in knee joint biomechanics during stair negotiation observed in our study need to be investigated further to help explain mechanisms behind the potential benefits of a sleeve knee brace for painful patellofemoral joint osteoarthritis.

The non-invasive evaluation technique of patellofemoral joint stress: a systematic literature review

Introduction: Patellofemoral joint stress (PFJS) is an important parameter for understanding the mechanism of patellofemoral joint pain, preventing patellofemoral joint injury, and evaluating the therapeutic efficacy of PFP rehabilitation programs. The purpose of this systematic review was to identify and categorize the non-invasive technique to evaluate the PFJS. Methods: Literature searches were conducted from January 2000 to October 2022 in electronic databases, namely, PubMed, Web of Science, and EBSCO (Medline, SPORTDiscus). This review includes studies that evaluated the patellofemoral joint reaction force (PJRF) or PFJS, with participants including both healthy individuals and those with patellofemoral joint pain, as well as cadavers with no organic changes. The study design includes cross-sectional studies, case-control studies, and randomized controlled trials. The JBI quality appraisal criteria tool was used to assess the risk of bias in the included studies. Results: In total, 5016 articles were identified in the database research and the citation network, and 69 studies were included in the review. Discussion: Researchers are still working to improve the accuracy of evaluation for PFJS by using a personalized model and optimizing quadriceps muscle strength calculations. In theory, the evaluation method of combining advanced computational and biplane fluoroscopy techniques has high accuracy in evaluating PFJS. The method should be further developed to establish the "gold standard" for PFJS evaluation. In practical applications, selecting appropriate methods and approaches based on theoretical considerations and ecological validity is essential.

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.

The effect of heel-to-toe drop of running shoes on patellofemoral joint stress during running

BACKGROUND

Traditional running shoes with heel-to-toe drops is thought to be a contributor to increased patellofemoral joint stress, which is proposed as a mechanism of patellofemoral pain.

RESEARCH QUESTION

Is there an increase in patellofemoral joint stress when running in shoes with drops compared to running in shoes without a drop?

METHODS

Lower limbs kinematics and ground reaction force were collected from eighteen healthy runners during over-ground running in shoes with 15 mm, 10 mm, 5 mm drops, and without a drop. Patellofemoral joint force and stress were calculated from the kinematic and kinetic data using a biomechanical model of the patellofemoral joint.

RESULTS

The peak patellofemoral joint stress was increased by more than 15% when running in shoes with 15 mm and 10 mm drops compared to running in shoes without a drop (p = 0.003, p = 0.001). The knee flexion angle was significantly increased when running in shoes with 15 mm, 10 mm and 5 mm drops (p = 0.014, p = 0.003, p = 0.002), the knee extension moment (p = 0.009, p = 0.002) and patellofemoral joint force (p = 0.003, p = 0.001) were increased when running in shoes with 15 mm and 10 mm drops, compared to running in shoes without a drop.

SIGNIFICANCE

Compared to running in shoes without a drop, running in shoes with drops > 5 mm increase the peak patellofemoral joint stress significantly, which is mainly due to the increased knee extension moment.

May the force be with you: understanding how patellofemoral joint reaction force compares across different activities and physical interventions-a systematic review and meta-analysis

OBJECTIVE

To systematically review and synthesise patellofemoral joint reaction force (PFJRF) in healthy individuals and those with patellofemoral pain and osteoarthritis (OA), during everyday activities, therapeutic exercises and with physical interventions (eg, foot orthotics, footwear, taping, bracing).

DESIGN

A systematic review with meta-analysis.

DATA SOURCES

Medline, Embase, Scopus, CINAHL, SportDiscus and Cochrane Library databases were searched.

ELIGIBILITY CRITERIA

Observational and interventional studies reporting PFJRF during everyday activities, therapeutic exercises, and physical interventions.

RESULTS

In healthy individuals, the weighted average of mean (±SD) peak PFJRF for everyday activities were: walking 0.9±0.4 body weight (BW), stair ascent 3.2±0.7 BW, stair descent 2.8±0.5 BW and running 5.2±1.2 BW. In those with patellofemoral pain, peak PFJRF were: walking 0.8±0.2 BW, stair ascent 2.5±0.5 BW, stair descent 2.6±0.5 BW, running 4.1±0.9 BW. Only single studies reported peak PFJRF during everyday activities in individuals with patellofemoral OA/articular cartilage defects (walking 1.3±0.5 BW, stair ascent 1.6±0.4 BW, stair descent 1.0±0.5 BW). The PFJRF was reported for many different exercises and physical interventions; however, considerable variability precluded any pooled estimates.

SUMMARY

Everyday activities and exercises involving larger knee flexion (eg, squatting) expose the patellofemoral joint to higher PFJRF than those involving smaller knee flexion (eg, walking). There were no discernable differences in peak PFJRF during everyday activities between healthy individuals and those with patellofemoral pain/OA. The information on PFJRF may be used to select appropriate variations of exercises and physical interventions.

Is patellofemoral pain preventable? A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effectiveness of interventions to reduce the risk of incident patellofemoral pain.

DESIGN

Systematic review and meta-analysis, with strength of evidence evaluated separately for each intervention type.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, Web of Science and SPORTDiscus.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials evaluating the effectiveness of interventions to reduce patellofemoral pain risk compared with a control/non-exposed group.

RESULTS

Thirteen trials of mostly military recruits and young athletes analysed six different interventions. There was low certainty evidence from two trials (227 participants) that patellofemoral braces worn during physical activity (compared with no brace) effectively reduced the risk of patellofemoral pain (risk ratio (RR) 0.40, 95% CI 0.22 to 0.73; I2=24.0%). There was low certainty evidence from one trial (320 participants) that running technique retraining to (run softer) reduced patellofemoral pain risk (RR 0.21, 95% CI 0.07 to 0.60). There was low certainty evidence from four trials (3364 participants) that multicomponent (strengthening/neuromuscular) exercise programmes did not significantly reduce the risk of patellofemoral pain (RR 0.49, 95% CI 0.18 to 1.36; I2=64.9%), although broad CIs may reflect exercise dose variations among studies. There was very low certainty evidence from four trials (2314 participants) that foot orthoses (compared with flat inserts/no orthosis) did not significantly reduce the risk of patellofemoral pain (RR 0.63, 95% CI 0.35 to 1.13; I2=0.0%). Static stretching and a running programme that progressed intensity (compared with volume) did not significantly influence patellofemoral pain risk (single studies).

CONCLUSION

There is low-level evidence that patellofemoral braces and running technique retraining can reduce the risk of patellofemoral pain by 60%-79%.

A mathematical modelling study investigating the influence of knee joint flexion angle and extension moment on patellofemoral joint reaction force and stress

BACKGROUND

Patellofemoral pain (PFP) is the most common orthopaedic condition among runners. Individuals with PFP exhibit greater patellofemoral joint (PFJ) reaction force and stress when compared with pain-free controls. However, it is not clear whether PFJ reaction force and stress are the highest (or lowest) when knee joint flexion angle and extension moment are in which combinations. We aimed to investigate the influence of knee joint flexion angle and extension moment on PFJ reaction force and stress.

METHODS

A PFJ sagittal model was used to quantify PFJ reaction force and stress. Based on the public dataset of the previous study, peak knee joint flexion angle and extension moment at various running speeds was calculated. Based on the calculated peak value, simulation ranges were set to knee joint flexion angle of 10-45° and extension moment of 0-240 Nm. The quadriceps force, effective lever arm length at quadriceps muscle, and PFJ contact area were determined as a function of the knee joint flexion angle and extension moment, and finally PFJ forces and stress were estimated.

RESULTS

PFJ reaction force increased as the knee flexion angle and extension moment increased. Although PFJ stress also increased as the knee extension moment increased, it was at the highest and lowest at 10° and about 30° knee joint flexion angles, respectively.

CONCLUSIONS

Incorporating knee flexion posture (approximately 30°) during running may help in reducing PFJ stress, which would be useful in the prevention of pain and act as an optimal treatment program for PFP.

The influence of sagittal trunk posture on the magnitude and rate of patellofemoral joint stress during stair ascent in asymptomatic females

BACKGROUND

Excessive patellofemoral joint stress (PFJS) is thought to be a contributory factor to patellofemoral pain (PFP). Thus, treatment strategies that minimize PFJS rate and magnitude during painful activities like stair ascent may be useful for optimizing outcomes for PFP patients. Sagittal plane trunk posture has been shown to influence PFJS during running although it is unknown if a similar relationship exists during stair ascent.

RESEARCH QUESTION

Does altering sagittal plane trunk posture affect PFJS rate and/or magnitude during stair ascent?

METHODS

Twenty asymptomatic females (23.4±2.5 yr; height: 164.4±7.9 cm; mass: 63.0±12.2 kg) performed 5 stair ascent trials (96 steps/min) during 3 conditions: self-selected trunk (SS), flexed trunk (FLX), and extended trunk (EXT). Three-dimensional kinematics (200 Hz) and ground reaction forces (2000 Hz) were collected during each trial. A previously described mathematical model was used to calculate PFJS that included subject-specific and non-subject-specific model inputs. Dependent variables included sagittal plane trunk angle, and the rates and magnitudes of PFJS, patellofemoral joint reaction force (PFJRF), and PFJ contact area during the stance phase of stair ascent.

RESULTS

Compared to SS, peak PFJS decreased during FLX (mean difference (MD)=2.6 MPa; p<0.001; 95%CI=2.2 to 2.9; effect size (ES)=5.2) and increased during EXT (MD=-3.3 MPa; p<0.001; 95%CI=-3.9 to -2.6; ES=-3.4). Similarly, PFJS rate decreased during FLX (MD=17.8 MPa/sec; p<0.001; 95%CI=13.6 to 21.9; ES=3.6) and increased during EXT (MD=-14 MPa/sec; 95%CI=-19.4 to -8.7; p<0.001; ES=-2.2).

SIGNIFICANCE

Sagittal plane trunk posture influences PFJS rate and magnitude during stair ascent in asymptomatic females. Increasing and decreasing forward trunk flexion resulted in decreased and increased PFJS respectively. Future studies should examine the effects of these movement strategy modifications on pain and function in patients with PFP.

RANDOMIZED PROSPECTIVE STUDY ON THE TREATMENT OF FEMORO-PATELLAR OSTEOARTHRITIS USING BRACING

OBJECTIVE

To compare the effect of a brace designed to stabilize the patellofemoral joint to that of a patella-shaped neoprene sleeve with patella cut out in patients with patellofemoral osteoarthritis.

METHODS

Fifty-seven patients with femoro-patellar osteoarthritis were allocated to two groups: patients with femoro-patellar functional brace and those with a neoprene knee with a patellar orifice. Both groups underwent clinical treatment of osteoarthritis and used medications daily 1 month before and up to 3 months after brace placement. They were evaluated with the WOMAC and Lequesne questionnaires and performed five times sit to stand test, Timed Up and Go test, and six minutes walk test immediately before and 1 and 3 months after brace placement.

RESULTS

Both groups had improved pain, stiffness, and function with no difference between groups. Drug use decreased in both groups in the first month but increased in the third month. Naproxen use was progressively higher in the control group.

CONCLUSION

Both knee orthoses improved pain and function and altered drug use only in the first month. Functional knee brace provided analgesia without increased use of naproxen. Level of Evidence IB, Randomized clinical trial.

Methods to assess patellofemoral joint stress: A systematic review

Changes in patellofemoral joint (PFJ) stress are related to the development and course of PFJ dysfunctions. Different methods for PFJ stress calculation have been used, making the comparison of PFJ stress values across different studies difficult. The purpose of this study was to systematically review the methods for PFJ stress calculation and highlight the differences among the methods. A systematic literature search was conducted in Medline, Embase, CINAHL, SPORTDiscus and Web of Science databases. Included studies examined PFJ stress in subjects with or without musculoskeletal conditions. Of 12,670 identified studies, 53 were included, with a total of 1134 subjects evaluated. The main differences among the methods to calculate PFJ stress were: i) method to calculate PFJ contact area; ii) method to calculate a constant (coefficient k) that defines the relation between quadriceps force and PFJ reaction force; iii) the inclusion of adjustments for sagittal plane forces. Considerable variability in PFJ stress results was observed. The greatest PFJ stress value was 55.03 MPa during a dance jump and the lowest value was 1.9 MPa during walking at the speed of 1.4 m/s. Most studies applied methods which use data from previous studies. However, methods which use data from their own participants for most parts of the calculation might be preferred to minimize potential errors. When direct measures are not possible, a standard method could be applied to facilitate comparisons among studies.

The coupled effects of crouch gait and patella alta on tibiofemoral and patellofemoral cartilage loading in children

BACKGROUND

Elevated tibiofemoral and patellofemoral loading in children who exhibit crouch gait may contribute to skeletal deformities, pain, and cessation of walking ability. Surgical procedures used to treat crouch frequently correct knee extensor insufficiency by advancing the patella. However, there is little quantitative understanding of how the magnitudes of crouch and patellofemoral correction affect cartilage loading in gait.

METHODS

We used a computational musculoskeletal model to simulate the gait of twenty typically developing children and fifteen cerebral palsy patients who exhibited mild, moderate, and severe crouch. For each walking posture, we assessed the influence of patella alta and baja on tibiofemoral and patellofemoral cartilage contact.

RESULTS

Tibiofemoral and patellofemoral contact pressures during the stance phase of normal gait averaged 2.2 and 1.0 MPa. Crouch gait increased pressure in both the tibofemoral (2.6-4.3 MPa) and patellofemoral (1.8-3.3 MPa) joints, while also shifting tibiofemoral contact to the posterior tibial plateau. For extended-knee postures, normal patellar positions (Insall-Salvatti ratio 0.8-1.2) concentrated contact on the middle third of the patellar cartilage. However, in flexed knee postures, both normal and baja patellar positions shifted pressure toward the superior edge of the patella. Moving the patella into alta restored pressure to the middle region of the patellar cartilage as crouch increased.

CONCLUSIONS

This work illustrates the potential to dramatically reduce tibiofemoral and patellofemoral cartilage loading by surgically correcting crouch gait, and highlights the interaction between patella position and knee posture in modulating the location of patellar contact during functional activities.

Gait Kinematics in Individuals with Acute and Chronic Patellofemoral Pain

PURPOSE

This study aimed to identify the discriminating kinematic gait characteristics between individuals with acute and chronic patellofemoral pain (PFP) and healthy controls.

METHODS

Ninety-eight runners with PFP (39 male, 59 female) and 98 healthy control runners (38 male, 60 female) ran on a treadmill at a self-selected speed while three-dimensional lower limb kinematic data were collected. Runners with PFP were split into acute (n = 25) and chronic (n = 73) subgroups on the basis of whether they had been experiencing pain for less or greater than 3 months, respectively. Principal component analysis and linear discriminant analysis were used to determine the combination of kinematic gait characteristics that optimally separated individuals with acute PFP and chronic PFP and healthy controls.

RESULTS

Compared with controls, both the acute and chronic PFP subgroups exhibited greater knee flexion across stance and greater ankle dorsiflexion during early stance. The acute PFP subgroup demonstrated greater transverse plane hip motion across stance compared with healthy controls. In contrast, the chronic PFP subgroup demonstrated greater frontal plane hip motion, greater knee abduction, and reduced ankle eversion/greater ankle inversion across stance when compared with healthy controls.

CONCLUSIONS

This study identified characteristics that discriminated between individuals with acute and chronic PFP when compared with healthy controls. Certain discriminating characteristics were shared between both the acute and chronic subgroups when compared with healthy controls, whereas others were specific to the duration of PFP.

International patellofemoral osteoarthritis consortium: Consensus statement on the diagnosis, burden, outcome measures, prognosis, risk factors and treatment

OBJECTIVE

To present the current status of knowledge in the field of patellofemoral (PF) osteoarthritis (OA) and formulate a research agenda in order to guide future research on this topic.

DESIGN

A 1-day meeting was organized with the aim to bring together international experts in the field to discuss the current state of knowledge on PF OA. Experts from multiple disciplines were invited based on their scientific publications in the field of PF OA and interest in the subject. Topics discussed include the diagnosis, impact, prognosis, and treatment of PF OA.

METHODS

Following context-setting presentations, an interactive discussion was held in order to achieve consensus on the PF OA topics of interest: (1) diagnosis and definition; (2) burden; (3) outcome measures; (4) prognosis; (5) risk factors, and (6) treatment. Groups of meeting attendees reviewed the literature on these topics and narratively summarized the current state of knowledge, and each group formulated research agenda items relevant to the specific topics of interest. Each consortium member consequently ranked the importance of all items on a 0-10 Numerical Rating Scale (NRS) (10 = extremely important, to 0 = not at all important).

RESULTS

After ranking all formulated items on importance, 6 of the 28 research agenda items formulated received an average of 7.5 points on the NRS. The most highly ranked items covered the fields of treatment, diagnosis, and definition of PF OA.

CONCLUSIONS

We recommend to develop clear clinical criteria for PF OA and to reach consensus on the definition of PF OA by both radiographs and MRI. Additionally, more understanding is necessary to be able to distinguish PF symptoms from those arising from the tibiofemoral joint. More insight is needed on effective treatment strategies for PF OA; specifically, tailoring nonpharmacological treatments to individuals with PF OA, and determining whether isolated PF OA requires different treatment strategies than combined PF and tibiofemoral OA.

Normalized patellofemoral joint reaction force is greater in individuals with patellofemoral pain

Patellofemoral pain is a disabling, highly prevalent pathology. Altered patellofemoral contact forces are theorized to contribute to this pain. Musculoskeletal modeling has been employed to better understand the etiology of patellofemoral pain. Currently, there are no data on the effective quadriceps moment arm for individuals with patellofemoral pain, forcing researchers to apply normative values when modeling such individuals. In addition, the ratio of patellofemoral reaction force to quadriceps force is often used as a surrogate for patellofemoral joint contact force, ignoring the fact that the quadriceps efficiency can vary with pathology and intervention. Thus, the purposes of this study were to: (1) quantify the effective quadriceps moment arm in individuals with patellofemoral pain and compare this value to a control cohort and (2) develop a novel methodology for quantifying the normalized patellofemoral joint reaction force in vivo during dynamic activities. Dynamic MR data were captured as subjects with patellofemoral pain (30F/3M) cyclically flexed their knee from 10° to 40°. Data for control subjects (29F/9M) were taken from a previous study. The moment arm data acquired across a large cohort of individuals with patellofemoral pain should help advance musculoskeletal modeling. The primary finding of this study was an increased mean normalized patellofemoral reaction force of 14.9% (maximum values at a knee angle of 10°) in individuals with patellofemoral pain. Understanding changes in the normalized patellofemoral reaction force with pathology may lead to improvements in clinical decision making, and consequently treatments, by providing a more direct measure of altered patellofemoral joint forces.

Is the effectiveness of patellofemoral bracing modified by patellofemoral alignment and trochlear morphology?

Background

This study was performed to determine if the effectiveness of patellofemoral bracing as a treatment for patellofemoral osteoarthritis is influenced by patellofemoral joint alignment and trochlear morphology. We hypothesized that those with more extreme patellar malalignment would benefit more from bracing.

Methods

Thirty-eight patients who had received bracing as part of a comprehensive treatment plan for patellofemoral osteoarthritis were selected for this study. Ten measures of patellar alignment were taken from X-rays. These alignment measures were divided into percentile groups (tertiles) for contingency table analysis. Treatment outcome was measured by Western Ontario and Macmasters Universities Osteoarthritis Index (WOMAC) scores and these were dichotomised into two groups according to “Improved” or “Not Improved” according to the minimum clinically important difference (MCID). Spearman’s rho test was performed for continuous variables and Fisher’s exact test was performed for correlation between tertile groups and MCID categories.

Results

Thirty-eight patients (9 male and 29 female) between the ages of 51 to 89 were included in this study. WOMAC scores ranged from −25 to 41.67, with a mean change of −3.97, 31.6, 44.7 and 31.6% of patients falling into the “Improved” group for Global, Pain and Function scores respectively. We found a non-significant trend shown (p = 0.058, correlation coefficient 0.31) between bisect offset and change in WOMAC global, indicating a trend for higher change in WOMAC scores with increasing bisect offset. Statistically significant correlations were found between mean MCID categories for the WOMAC global and function groups when analysed against percentile groups for bisect offset (p < 0.01) and patellar subluxation distance (p < 0.05), indicating those in higher percentile groups were more likely not to improve after six months.

Conclusion

Higher bisect offset and patellar subluxation distance measures were associated with poorer outcomes. However, due to the limited sample size, more studies are required to fully examine this relationship.

Effects of Patellofemoral Taping on Patellofemoral Joint Alignment and Contact Area During Weight Bearing

Study Design Controlled laboratory study. Background Although it has been theorized that patellofemoral joint (PFJ) taping can correct patellar malalignment, the effects of PFJ taping techniques on patellar alignment and contact area have not yet been studied during weight bearing. Objective To examine the effects of 2 taping approaches (Kinesio and McConnell) on PFJ alignment and contact area. Methods Fourteen female subjects with patellofemoral pain and PFJ malalignment participated. Each subject underwent a pretaping magnetic resonance imaging (MRI) scan session and 2 MRI scan sessions after the application of the 2 taping techniques, which aimed to correct lateral patellar displacement. Subjects were asked to report their pain level prior to each scan session. During MRI assessment, subjects were loaded with 25% of body weight on their involved/more symptomatic leg at 0°, 20°, and 40° of knee flexion. The outcome measures included patellar lateral displacement (bisect-offset [BSO] index), mediolateral patellar tilt angle, patellar height (Insall-Salvati ratio), contact area, and pain. Patellofemoral joint alignment and contact area were compared among the 3 conditions (no tape, Kinesio, and McConnell) at 3 knee angles using a 2-factor, repeated-measures analysis of variance. Pain was compared among the 3 conditions using the Friedman test and post hoc Wilcoxon signed-rank tests. Results Our data did not reveal any significant effects of either McConnell or Kinesio taping on the BSO index, patellar tilt angle, Insall-Salvati ratio, or contact area across the 3 knee angles, whereas knee angle had a significant effect on the BSO index and contact area. A reduction in pain was observed after the application of the Kinesio taping technique. Conclusion In a weight-bearing condition, this preliminary study did not support the use of PFJ taping as a medial correction technique to alter the PFJ contact area or alignment of the patella. J Orthop Sports Phys Ther 2017;47(2):115-123. doi:10.2519/jospt.2017.6936.

A knee brace alters patella position in patellofemoral osteoarthritis: a study using weight bearing magnetic resonance imaging

OBJECTIVE

To assess using weight bearing magnetic resonance imaging (MRIs), whether a patellar brace altered patellar position and alignment in patellofemoral joint (PFJ) osteoarthritis (OA).

DESIGN

Subjects age 40-70 years old with symptomatic and a radiographic Kellgren-Lawrence (K-L) evidence of PFJOA. Weight bearing knee MRIs with and without a patellar brace were obtained using an upright open 0.25 T scanner (G-Scan, Easote Biomedica, Italy). Five aspects of patellar position were measured: mediolateral alignment by the bisect offset index, angulation by patellar tilt, patellar height by patellar height ratio (patellar length/patellar tendon length), lateral patellofemoral (PF) contact area and finally a measurement of PF bony separation of the lateral patellar facet and the adjacent surface on the femoral trochlea (Fig. 1).

RESULTS

Thirty participants were recruited (mean age 57 SD 27.8; body mass index (BMI) 27.8 SD 4.2); 17 were females. Four patients had non-usable data. Main analysis used paired t tests comparing within subject patellar position with and without brace. For bisect offset index, patellar tilt and patellar height ratio there were no significant differences between the brace and no brace conditions. However, the brace increased lateral facet contact area (P = .04) and decreased lateral PF separation (P = .03).

CONCLUSION

A patellar brace alters patellar position and increases contact area between the patella and femoral trochlea. These changes would lower contact stress at the PFJ. Such changes in patella position in weight bearing provide a possible biomechanical explanation for the success of the PFJ brace in clinical trials on PFJOA.

A randomised trial of a brace for patellofemoral osteoarthritis targeting knee pain and bone marrow lesions

Objective

Braces used to treat (PF) osteoarthritis (OA) may reduce contact stress across the PF joint. We hypothesised that in PF OA, braces would decrease knee pain and shrink PF bone marrow lesions (BMLs).

Methods

Eligible subjects had painful PF OA. Subjects were randomly allocated to brace or no brace for 6 weeks. Knee MRIs were acquired at baseline and 6 weeks. We measured BMLs on post-contrast fat suppressed sagittal and proton density weighted axial images. The primary symptom outcome was change in pain at 6 weeks during a preselected painful activity, and the primary structural outcome was BML volume change in the PF joint. Analyses used multiple linear regression.

Results

We randomised 126 subjects aged 40–70 years (mean age 55.5  years; 72 females (57.1%)). Mean nominated visual analogue scale (0–10 cm) pain score at baseline was 6.5 cm. 94 knees (75%) had PF BMLs at baseline. Subjects wore the brace for a mean of 7.4 h/day. 6 subjects withdrew during the trial. After accounting for baseline values, the brace group had lower knee pain than the control group at 6 weeks (difference between groups −1.3 cm, 95% CI −2.0 to −0.7; p<0.001) and reduced PF BML volume (difference −490.6 mm³, 95% CI −929.5 to −51.7; p=0.03) but not tibiofemoral volume (difference −53.9 mm³, 95% CI −625.9 to 518.2; p=0.85).

Conclusions

A PF brace reduces BML volume in the targeted compartment of the knee, and relieves knee pain.

Trial registration number

UK. ISRCTN50380458.

Comparison of Three-Dimensional Patellofemoral Joint Reaction Forces in Persons With and Without Patellofemoral Pain

The purpose of this study was to determine if persons with patellofemoral pain (PFP) exhibit differences in patellofemoral joint reaction forces (PFJRFs) during functional activities. Forty females (20 PFP, 20 controls) underwent two phases of data collection: (1) magnetic resonance imaging (MRI) and (2) biomechanical analysis during walking, running, stair ascent, and stair descent. A previously described three-dimensional model was used to estimate PFJRFs. Resultant PFJRFs and the orthogonal components were reported. The PFP group demonstrated lower peak resultant PFJRFs and posterior component and superior component of the PFJRFs compared with the control group across all conditions. However, the PFP group had a higher peak lateral component of the PFJRF in three out of the four conditions evaluated. The lower resultant PFJRFs suggested that individuals with PFP may employ strategies to minimize patellofemoral joint loading, but it did not result in diminished lateral forces acting on the patella.

The effect of patellofemoral bracing on walking in individuals with patellofemoral pain syndrome

BACKGROUND

Although knee braces are used by individuals with patellofemoral pain syndrome, the effect of patellofemoral bracing on knee flexion during walking has not been elucidated.

AIM

The purpose of this study was to evaluate the effect of patellofemoral bracing on sagittal plane knee joint kinematics and temporal spatial parameters during walking in individuals with patellofemoral pain syndrome.

STUDY DESIGN

Quasi-experimental.

METHODS

Ten subjects with a diagnosis of patellofemoral pain syndrome were fitted with a knee brace incorporating an infrapatellar strap. Testing was performed at baseline and after 6 weeks of use. Gait analysis and a visual analog scale were used to assess outcomes in this study.

RESULTS

A 59.6% decrease in pain was reported by using bracing. Bracing significantly improved speed of walking (p ≤ 0.001) and step length (p ≤ 0.001). The mean cadence was also increased following 6 weeks of patellofemoral brace use, but this was not significant (p = 0.077). Knee flexion angles improved during initial contact, loading response, and mid-swing (p ≤ 0.001) after 6 weeks of patellofemoral brace use.

CONCLUSION

Knee orthoses resulted in decreased pain, improved temporal spatial parameters (speed of walking and step length), and increased knee flexion angles during ambulation in patients with patellofemoral pain syndrome.

Offaxis neuromuscular training of knee injuries using an offaxis robotic elliptical trainer

The goal of this study was to use an offaxis robotic elliptical trainer to improve off-axis neuromuscular control in people with knee injuries. Thirteen individuals with knee injuries participated in the study. Among them, 8 individuals participated in 18 sessions of pivoting offaxis intensity-adjustable neuromuscular control training (POINT) (3 sessions/week for 6 weeks including 3 evaluation sessions) to improve offaxis neuromuscular control, specifically dynamic lower limb stability in pivoting. 5 individuals served as controls who only participated in the three evaluations. Following POINT patients in the training group reduced pivoting instability (p=0.024), while the control group did not (p=0.118). Individuals in the training group were able to hop farther in a single leg hop for distance task, take shorter in 12 m hop time for time task, and reported reduced knee pain. The results suggest that subject-specific POINT utilizing the novel robotic elliptical trainer can be implemented as a rehabilitation protocol for patients with knee injuries to improve their lower limb functions and reduce knee symptoms.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

The influence of heel height on patellofemoral joint kinetics during walking

Although wearing high-heeled shoes has long been considered a risk factor for the development for patellofemoral pain (PFP) in women, patellofemoral joint kinetics during high-heeled gait has not been examined. The purpose of this study was to determine if heel height increases patellofemoral joint loading during walking. Eleven healthy women (mean age 25.0±3.1 yrs) participated. Lower extremity kinematics and kinetics were obtained under 3 different shoe conditions: low heel (1.27 cm), medium heel (6.35 cm), and high heel (9.53 cm). Patellofemoral joint stress was estimated using a previously described biomechanical model. Model outputs included patellofemoral joint reaction force, patellofemoral joint stress and utilized contact area as a function of the gait cycle. One-way ANOVAs with repeated measures were used to compare the model outputs and knee joint angles among the 3 shoe conditions. Peak patellofemoral joint stress was found to increase significantly (p=0.002) with increasing heel height (low heel: 1.9±0.7 MPa, medium heel: 2.6±1.2 MPa, and high heel: 3.6±1.5 MPa). The increased patellofemoral joint stress was mainly driven by an increase in joint reaction force owing to higher knee extensor moments and knee flexion angles. Our findings support the premise that wearing high-heeled shoes may be a contributing factor with respect to the development of PFP.

MRI-based modeling for radiocarpal joint mechanics: validation criteria and results for four specimen-specific models

The objective of this study was to validate the MRI-based joint contact modeling methodology in the radiocarpal joints by comparison of model results with invasive specimen-specific radiocarpal contact measurements from four cadaver experiments. We used a single validation criterion for multiple outcome measures to characterize the utility and overall validity of the modeling approach. For each experiment, a Pressurex film and a Tekscan sensor were sequentially placed into the radiocarpal joints during simulated grasp. Computer models were constructed based on MRI visualization of the cadaver specimens without load. Images were also acquired during the loaded configuration used with the direct experimental measurements. Geometric surface models of the radius, scaphoid and lunate (including cartilage) were constructed from the images acquired without the load. The carpal bone motions from the unloaded state to the loaded state were determined using a series of 3D image registrations. Cartilage thickness was assumed uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Validation was based on experimental versus model contact area, contact force, average contact pressure and peak contact pressure for the radioscaphoid and radiolunate articulations. Contact area was also measured directly from images acquired under load and compared to the experimental and model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape and location of radioscaphoid and radiolunate contact regions. Quantitative data from the model generally compared well with the experimental data for all specimens. Contact area from the MRI-based model was very similar to the contact area measured directly from the images. For all outcome measures except average and peak pressures, at least two specimen models met the validation criteria with respect to experimental measurements for both articulations. Only the model for one specimen met the validation criteria for average and peak pressure of both articulations; however the experimental measures for peak pressure also exhibited high variability. MRI-based modeling can reliably be used for evaluating the contact area and contact force with similar confidence as in currently available experimental techniques. Average contact pressure, and peak contact pressure were more variable from all measurement techniques, and these measures from MRI-based modeling should be used with some caution.

PRELIMINARY VALIDATION OF MRI-BASED MODELING FOR EVALUATION OF JOINT MECHANICS

The objective of this study was to perform preliminary validation of MRI-based joint contact modeling methodology in the radiocarpal joints by comparison with the results of invasive radiocarpal contact measurements in three cadaver experiments. For each experiment, either Pressurex film or a Tekscan sensor was placed into the radiocarpal joints during a simulated grasp. Computer models were based on magnetic resonance imaging (MRI) of the cadaver specimens without load as well as on images acquired with the same loading used for the direct measurements. Geometric surface models of the radius, scaphoid, and lunate (including cartilage) were constructed from the images acquired without load. The carpal bone motions from the unloaded to the loaded state were determined using three-dimensional (3D) voxel image registration. Cartilage thickness was assumed to be uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Resulting data included peak contact pressure, contact area, and contact force in the radioscaphoid and radiolunate joints. Contact area was also measured directly from MR images acquired with load and compared to model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape, and location of radioscaphoid and radiolunate contact areas. Quantitative comparison of model and experimental data was reasonable, but less consistent. Contact area from the MRI-based model was always similar to the contact area measured directly from the MR images. With additional experiments, we believe that MRI-based joint contact modeling will soon be fully validated in the radiocarpal joints.

Foot biomechanics and initial effects of infrapatellar strap on gait parameters in patients with unilateral patellofemoral pain syndrome

BACKGROUND

There is limited information on the relationship between plantar foot pressure and patellofemoral pain syndrome (PFPS). In addition, there is not enough research on the effects of an infrapatellar strap on PFPS.

OBJECTIVE

The aim of this study was to evaluate the immediate effects of an infrapatellar strap on dynamic pedabarography in patients with unilateral PFPS.

METHODS

Clinical case control study design. 18 females subjects with unilateral PFPS were included in the study. Gait parameters were tested using pedabarography during barefoot walking with and without an infrapatellar strap.

RESULTS

There were no statistically significant differences in gait trials comparing infrapatellar strap to no strap (P>0.05). In addition, a significant difference (P=0.043) in the % forefoot surface on the involved side demonstrated that body weight is transferred to medial aspect of the foot.

DISCUSSION

Although our results show a difference between the forefoot surface % of the affected and unaffected sides of subjects with PFPS there was no indication that an infrapatellar strap had any immediate effect on this parameter.

CONCLUSION

It is not clear whether PFPS is a cause or effect of abnormal gait. Further research is warranted to investigate the long-term effects of wearing an infrapatellar strap and associated altered foot biomechanics due to PFPS.

Treatment of patella alta with taping, exercise, mobilization, and functional activity modification: a case report

Knee pain associated with patella alta (PA) can limit involvement in sport or work activities and prevent an individual from performing basic functional tasks. This case report describes the use of patellar taping to treat an individual with PA. The patient was a 56 year-old female with bilateral knee pain associated with PA. The focus of treatment was to decrease pain during functional activities by using tape to correct patella alignment. The patient was also instructed on specific exercises and mobilizations. The primary outcome measure was the ADL subscale of the Knee Outcome Survey (ADL-KOS). Initially, the patient scored a 50 on the ADL-KOS and rated her function at 30% of normal. She demonstrated symptom improvement when tape was applied appropriately and was, therefore, instructed in tape application. At discharge, the patient scored a 56 on the ADL-KOS and rated her function at 70% of normal. This case demonstrates the effective use of a taping method for the treatment of pain associated with PA. Taping appears to be a safe, conservative, and cost-efficient measure to manage symptoms and to improve activity tolerance in this patient.

A randomized trial of patellofemoral bracing for treatment of patellofemoral osteoarthritis

PURPOSE

The number of effective knee osteoarthritis (OA) interventions, especially those tailored to specific compartmental involvement, are small. The objective of this study was to determine the efficacy of a realigning patellofemoral (PF) brace in improving pain and function among persons with symptomatic lateral PF OA.

METHOD

We conducted a double blind, randomized crossover trial of a realigning PF brace for persons with lateral PF OA. Participants had lateral PF OA with anterior knee symptoms on most days of the month, lateral PF joint space narrowing, and radiographic evidence of a definite osteophyte in the PF joint. We compared two treatments: (1) Control treatment consisting of a BioSkin Q Brace with patellar realigning strap removed; and (2) Active treatment consisting of a realigning BioSkin Q Brace with the strap applied. For each participant, the trial lasted 18 weeks, including 6 weeks each of active and control treatment period separated by a 6-week washout period. The order of treatments was randomized. The primary outcome was change in knee pain on the visual analog scale (VAS). Secondary outcomes included WOMAC pain, function, and stiffness. An unstructured correlation matrix for observations within participants was used in generalized estimating equation fitting to derive a linear regression model that expressed the relation between the intervention and change in VAS pain.

RESULTS

80 participants (63 F) with a mean age and body mass index of 61 years and 28 kg/m(2), respectively, were randomized by order of treatment. A model examining the main effects for change in VAS knee pain (0-100) demonstrated no significant treatment effect (-0.68 VAS units, 95% CI: -6.2, 4.8 units, P=0.81) and no differential carryover effect. There was also no significant difference between active and control treatments for WOMAC pain, function, or stiffness outcomes.

CONCLUSION

The effects of a specific realigning PF brace are not of clinical or statistical significance.

A clinical study of the biomechanics of step descent using different treatment modalities for patellofemoral pain

INTRODUCTION

In the previous study we have demonstrated that in healthy subjects significant changes in coronal and transverse plane mechanics can be produced by the application of a neutral patella taping technique and a patellar brace. Recently it has also been identified that patients with patellofemoral pain syndrome (PFPS) display alterations in gait in the coronal and transverse planes.

OBJECTIVE

This study investigated the effect of patellar bracing and taping on the three-dimensional mechanics of the knee of patellofemoral pain patients during a step descent task.

METHOD

Thirteen patients diagnosed with patellofemoral pain syndrome performed a slow step descent. This was conducted under three randomized conditions: (a) no intervention, (b) neutral patella taping, (c) patellofemoral bracing. A 20cm step was constructed to accommodate an AMTI force platform. Kinematic data were collected using a ten camera infra-red Oqus motion analysis system. Reflective markers were placed on the foot, shank and thigh using the Calibrated Anatomical System Technique (CAST).

RESULTS

The coronal plane knee range of motion was significantly reduced with taping (P=0.031) and bracing (P=0.005). The transverse plane showed a significant reduction in the knee range of motion with the brace compared to taping (P=0.032) and no treatment (P=0.046).

CONCLUSION

Patients suffering from patellofemoral pain syndrome demonstrated improved coronal plane and torsional control of the knee during slow step descent following the application of bracing and taping. This study further reinforces the view that coronal and transverse plane mechanics should not be overlooked when studying patellofemoral pain.

Quantification of Patellofemoral Joint Reaction Forces during Functional Activities Using a Subject-Specific Three-Dimensional Model

The purpose of this study was to describe an imaging based, subject specific model that was developed to quantify patellofemoral joint reaction forces (PFJRF’s). The secondary purpose was to test the model in a group of healthy individuals while performing various functional tasks. Twenty healthy subjects (10 males, 10 females) were recruited. All participants underwent two phases of data collection: 1) magnetic resonance imaging of the knee, patellofemoral joint, and thigh, and 2) kinematic, kinetic and EMG analysis during walking, running, stair ascent, and stair descent. Using data obtained from MRI, a subject specific representation of the extensor mechanism was created. Individual gait data were used to drive the model (via an optimization routine) and three-dimensional vasti muscle forces and subsequent three-dimensional PFJRF’s were computed. The average peak PFJRF was found to be highest during running (58.2 N/kg-bwt), followed by stair ascent (33.9 N/kg-bwt), stair descent (27.9 N/kg-bwt), and walking (10.1 N/kg-bwt). No differences were found between males and females. For all conditions, the direction of the PFJRF was always in the posterior, superior, and lateral directions. The posterior component of the PFJRF always had the greatest magnitude, followed by superior and lateral components. Our results indicate that estimates of the magnitude and direction of the PFJRF during functional tasks can be obtained using a 3D-imaging based model.

Gait and neuromuscular adaptations after using a feedback-based gait monitoring knee brace

PURPOSE

The purpose of this study was to evaluate the gait and neuromuscular effects of a feedback-based gait monitoring knee brace. The aim of this paper was to explore how training with this knee brace affected the gait pattern utilized, rate of loading (ROL), and proprioceptive acuity.

METHODS

Fifteen healthy women wore this knee brace that provided audible feedback on gait kinematics for a 30-min training period. We performed pre- and post-gait analyses and proprioceptive acuity assessments to determine gait learning and adaptation with this training.

RESULTS

Post-training significant changes were seen in the knee angle prior to and at initial contact and peak knee extensor, flexor, and adductor moments, which ultimately led to a reduced ROL experienced. Subjects also had improved proprioceptive acuity post-training.

INTERPRETATIONS

Our results indicate that using a feedback-based gait monitoring knee brace can change the gait pattern by increasing the knee flexion angle during the swing to stance transition. Though there was an approximate 25% decrease in the ROL experienced, there was also an increase in the knee adductor moment. Future long-term studies are needed to further explore the positive and negative effects of feedback-based gait monitoring knee brace on individuals with a compromised knee joint, such as those post-anterior cruciate ligament injury.

Dynamic in vivo quadriceps lines-of-action

Tissue stresses and quadriceps forces are crucial factors when considering knee joint biomechanics. However, it is difficult to obtain direct, in vivo, measurements of these quantities. The primary purpose of this study was to provide the first complete description of quadriceps geometry (force directions and moment arms) of individual quadriceps components using in vivo, 3D data collected during volitional knee extension. A secondary purpose was to determine if 3D quadriceps geometry is altered in patients with patellofemoral pain and maltracking. After obtaining informed consent, cine-phase contrast (PC) MRI sets (x,y,z velocity and anatomic images) were acquired from 25 asymptomatic knees and 15 knees with patellofemoral pain during active knee extension. Using a sagittal-oblique and two coronal-oblique imaging planes, the origins and insertions of each quadriceps line-of-action were identified and tracked throughout the motion by integrating the cine-PC velocity data. The force direction and relative moment (RM) were calculated for each line-of-action. All quadriceps lines-of-action were oriented primarily in the superior direction. There were no significant differences in quadriceps geometry between asymptomatic and subjects with patellofemoral pain. However, patellofemoral kinematics were significantly different between the two populations. This study will improve the ability of musculoskeletal models to closely match in vivo human performance by providing accurate 3D quadriceps geometry and associated patellofemoral kinematics during dynamic knee motion. Furthermore, determination that quadriceps geometry is not altered in patellofemoral pain supports the use of generalized a knee model based on asymptomatic quadriceps architecture.

The influence of reduced hamstring length on patellofemoral joint stress during squatting in healthy male adults

Increased patellofemoral joint (PFJ) stress has been implicated in the development of PFJ pathologies. Previous studies have identified a relationship between reduced hamstring length and patellofemoral pain syndrome. Hamstring stretching is also recommended in the management thereof. However, the relationship between reduced hamstring length and PFJ stress has not been explored in vivo during activities that load the PFJ, such as squatting. The objective of this study was to determine if persons with reduced hamstring length demonstrate increased PFJ stress during squatting compared with individuals without reduced hamstring length. Eight participants with, and eight participants without, reduced hamstring length were assessed to determine their PFJ contact area using magnetic resonance imaging, and their PFJ reaction force during squatting using motion analysis. Data collected were entered into a biomechanical model to calculate medial, lateral and total PFJ stress. It was found that participants with reduced hamstring length had significantly greater total (393.39 Pa/kg vs. 213.01 Pa/kg) and lateral (311.23 Pa/kg vs. 142.55 Pa/kg) PFJ stress at 60 degrees knee flexion during squat descent and ascent (427.75 Pa/kg vs. 255.64 Pa/kg and 337.75 Pa/kg vs. 170.63 Pa/kg, respectively). This was due to significantly increased PFJ reaction force at 60 degrees knee flexion during squat descent (12.18 N/kg vs. 7.21 N/kg) and ascent (13.03 N/kg vs. 8.72 N/kg), and lower medial PFJ contact area at 60 degrees knee flexion (88 mm(2) vs. 160 mm(2)). The results of this study demonstrate a relationship between reduced hamstring length and increased PFJ stress during squatting due to increased PFJ reaction force and reduced medial PFJ contact area.

Design and Validation of a Knee Brace With Feedback to Reduce the Rate of Loading

The repetitive nature of walking can lead to repetitive stress and associated complications due to the rate of loading (ROL) experienced by the body at the initial contact of the foot with the ground. An individual’s gait kinematics at initial contact has been suggested to give rise to the ROL, and a repetitive, high ROL may lead to several disorders, including osteoarthritis. We present the design, development, and validation of a knee brace that provides feedback to the user during gait. The feedback consists of an auditory signal when the specific parameters of knee angle or tibial acceleration 50 ms prior to contact are exceeded. Nine women were recruited for the gait analysis, and the gait characteristics with and without the brace and feedback are analyzed. Our results indicate that using a knee brace with feedback can effectively change the gait kinematics used during walking, leading to a reduced ROL experienced at initial contact. Using a knee brace with feedback is a novel approach to gait retraining. Al-though the kinetics of how the subjects change in gait pattern is unknown, the reduced ROL experienced is significant and warrants further investigation.

Developments in the clinical understanding of osteoarthritis

With the recognition that osteoarthritis is a disease of the whole joint, attention has focused increasingly on features in the joint environment which cause ongoing joint damage and are likely sources of pain. This article reviews current ways of assessing osteoarthritis progression and what factors potentiate it, structural abnormalities that probably produce pain, new understandings of the genetics of osteoarthritis, and evaluations of new and old treatments.

Identification of abnormal hip motion associated with acetabular labral pathology

STUDY DESIGN

Resident's case problem.

BACKGROUND

Recent literature has suggested that acetabular labral pathology secondary to femoroacetabular impingement (FAI) may be a precursor to early-onset hip osteoarthritis. The purpose of this resident's case problem was to explore the extent to which abnormal movement at the hip is a possible contributor to acetabular labral pathology.

DIAGNOSIS

The patient was a 25-year-old female with a 4-year history of anterior-medial groin pain. Based on a combination of the clinical examination and magnetic resonance imaging findings, she was given a diagnosis of acetabular labral tear by her orthopaedic surgeon and referred to a physical therapist for assessment. Movement analysis during a single-leg step down, running, and a drop jump maneuver revealed excessive hip adduction and internal rotation on the involved side, which reproduced her symptoms. Application of a hip-strapping device resulted in decreased hip adduction and internal rotation, and an immediate decrease in symptoms.

DISCUSSION

The reduction in pain secondary to controlling hip motion suggests that excessive frontal and transverse plane hip motions may contribute to FAI. Accordingly, physical therapy intervention aimed at controlling and reducing hip adduction and internal rotation during activities may be indicated in patients who present with this movement pattern associated with anterior hip/groin pain.

The influence of patellar bracing on patellar and knee load-distribution and kinematics: an experimental cadaver study

The aim of this study was to analyze the biomechanical consequences of patella bracing in order to evaluate possible mechanisms supporting its clinical application. The hypothesis is that the patellar bracing reduces patellofemoral pressure by influencing patellar and knee kinematics, and load distribution. Physiologic isokinetic knee extension motions were simulated on ten human knee cadaver specimens using a knee kinematic simulator. Joint kinematics were evaluated using an ultrasound-based motion analysis system and patellofemoral contact pressure was measured using a thin-film piezoresistive pressure measuring system. Infrapatellar tissue pressure was analyzed using a closed sensor-cell. Three different patella braces were fitted to the knee cadavers and their influence on the kinematic and kinetic biomechanical parameters were evaluated and compared to the physiologic situation. Patellar bracing resulted in a significant (p = 0.05) proximalization of the patella up to 3 mm. Depending on the type of brace used, a decrease in the infrapatellar fat pad pressure was found and the patellofemoral contact area was decreased significantly (p = 0.05) between 60 degrees of knee flexion and full extension (maximum 22%). Patella bracing significantly (p = 0.05) reduced the patellofemoral contact pressure an average of 10%, as well as the peak contact pressure which occurred. Patellar bracing significantly influences patella biomechanics in a reduction of the patellofemoral contact area and contact pressure as well as a decrease in the infrapatellar tissue pressure. The application of infrapatellar straps is suggested for the treatment and prevention of anterior knee pain, especially in high level sports.

Patella malalignment, pain and patellofemoral progression: the Health ABC Study

OBJECTIVE

Patellofemoral (PF) joint osteoarthritis (OA) is strongly correlated with lower extremity disability and knee pain. Risk factors for pain and structural progression in PF OA are poorly understood. Our objective was to determine the association between patella malalignment and its relation to pain severity, and PF OA disease progression.

METHODS

We conducted an analysis of data from the Health ABC knee OA study. Health ABC is a community based, multi-center cohort study of 3075 Caucasian and Black men and women aged 70-79 at enrollment. Weight bearing skyline knee X-rays were obtained in a subset (595) of subjects, with and without knee pain, at year 2 and year 5 (mean follow-up 36 months). Films were read paired, and PF osteophytes (OST) and joint space narrowing (JSN) were scored on a 0-3 scale using the Osteoarthritis Research Society International atlas. We defined progression of PF OA as any increase in JSN score. Three measures of patella malalignment were made: sulcus angle; patella tilt angle; and patella subluxation medially or laterally (bisect offset). Knee symptoms were assessed using a knee specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) knee pain subscale. We assessed the relationship between baseline patella malalignment and pain severity (linear regression for WOMAC) and compartment specific PF OA progression (logistic regression for dichotomous outcomes). We classified continuous measures of patella alignment into quartile groups. We performed multivariable adjusted logistic regression models, including age, gender and body mass index (BMI) to assess the relation of baseline patella alignment to the occurrence of PF JSN progression using generalized estimating equations (GEE).

RESULTS

The subjects had a mean age 73.6 (SD 2.9), BMI 28.8 (SD 4.9), 40.3% male, and 46% were Black. Medial displacement of the patella predisposed to medial JSN progression; odds for each quartile 1, 1.2, 1.2, 2.2 (P for trend=0.03), whilst protecting from lateral JSN progression; odds for each quartile 1, 0.7, 0.6, 0.4 (P for trend=0.0004). Increasing patella tilt protected from medial JSN progression; odds for each quartile 1, 0.8, 0.5, 0.2 (P<0.0001) and trended to increasing pain severity (P=0.09).

CONCLUSION

Patella malalignment is associated with PF disease progression. Medial displacement and tilt of the patella predisposes to medial JSN progression, whilst lateral displacement is predictive of lateral JSN progression. The influence of patella malalignment has important implications since it is potentially modifiable through footwear, taping and/or knee bracing.

Current evidence and clinical applications of therapeutic knee braces

Braces are commonly used for the management of musculoskeletal injuries. With improvements in design and application, the knee brace has gained recognition by many as a treatment and prevention modality. However, there exist many different categories of knee braces, leading to confusion among many end users. The theoretical basis of the mechanism of action of the unloader, prophylactic, patellofemoral, and functional knee braces are explained in this review. This article also provides an update on the various knee braces in terms of the clinical efficacy and appropriate prescription recommendations.

Surgical biomechanics of the patellofemoral joint

This review presents objective data, as far as possible, about the current understanding of the biomechanics of the patellofemoral joint as it pertains to the management of patellofemoral problems. When faced with a patellofemoral malfunction, it is important to check all the soft-tissue and articular geometry factors relating to the patella locally and not to neglect the overall lower limb alignment and function. It is important to remember that small alterations in alignment can result in significant alterations in patellofemoral joint stresses and that changes in the mechanics of the patellofemoral joint can also result in changes in the tibiofemoral compartments. Surgical intervention for patellofemoral problems needs to be planned carefully and take into account an individual's anatomy.

A Modeling Framework to Estimate Patellofemoral Joint Cartilage Stress In Vivo

PURPOSE

Patellofemoral (PF) pain is common among athletes and may be caused by increased subchondral bone stress as a result of increased stress in the cartilage of the femur or patella. This article presents a modeling pipeline to estimate in vivo cartilage stress in the PF joint.

METHODS

The modeling pipeline uses the finite element method to calculate stresses and strains in the PF joint cartilage. Model inputs include an accurate geometrical representation of the bones and cartilage from magnetic resonance imaging (MRI), cartilage material properties, and an estimate of muscle forces from an EMG-driven musculoskeletal model. Validation is performed using PF joint contact area and patellar orientation measured from upright, weight-bearing MRI. Preliminary data from an active, pain-free subject illustrate the modeling pipeline to calculate cartilage stress during a static squat.

RESULTS

The quasistatic finite element simulation reproduced the orientation of the patella to within 2.1 mm and predicted the PF joint contact area to within 2.3%. Octahedral shear stresses were highest in the central, lateral aspect of the patella cartilage with a peak of 2.5 MPa. The corresponding stresses in the femoral cartilage reached only 2.0 MPa. However, peak hydrostatic pressures were higher within the femoral cartilage (3.5 MPa) than the patellar cartilage (2.3 MPa).

CONCLUSION

The methods presented in this article offer a novel approach to calculate PF joint cartilage stress in vivo. Future efforts will use this modeling pipeline to further our knowledge of PF pain and potential rehabilitation strategies.

Effect of bracing on patellofemoral joint stress while ascending and descending stairs

OBJECTIVE

To test the hypothesis that individuals who respond favorably to bracing will exhibit decreased patellofemoral joint stress during stair ambulation.

DESIGN

A repeated-measures, cross-sectional study.

BACKGROUND

Ascending and descending stairs is one of the most painful activities of daily living for persons with patellofemoral pain (PFP). Although patellar bracing has been shown to reduce symptoms during such tasks, the underlying mechanism has not been identified.

METHODS

Fifteen subjects with a diagnosis of PFP completed 2 phases of data collection: (1) magnetic resonance imaging to determine patellofemoral joint contact area, and (2) gait analysis during stair ascent and descent. Data were obtained under braced and non-braced conditions. Variables obtained from both data collection sessions were used as input variables into a biomechanical model to quantify patellofemoral joint stress.

RESULTS

Although subjects reported an average decrease in pain of 56%, bracing did not reduce peak stress during stair ascent and descent. This finding can be explained by the fact that despite improvements in contact area, bracing resulted in greater knee extensor muscle moments and joint reaction forces.

CONCLUSIONS

Our results do not support the hypothesis that individuals with PFP would demonstrate reduced patellofemoral stress during stair ambulation following the application of a patellar brace.

CLINICAL RELEVANCE

Although bracing did not decrease patellofemoral joint stress during stair ascent and descent, the decrease in pain, increase in quadriceps utilization, and tolerance of joint reaction forces would appear to be beneficial consequences of bracing.