Predicting Musculoskeletal Loading at Common Running Injury Locations Using Machine Learning and Instrumented Insoles

INTRODUCTION

Wearables have the potential to provide accurate estimates of tissue loads at common running injury locations. Here we investigate the accuracy by which commercially available instrumented insoles (ARION; ATO-GEAR, Eindhoven, The Netherlands) can predict musculoskeletal loading at common running injury locations.

METHODS

Nineteen runners (10 males) ran at five different speeds, four slopes, with different step frequencies, and forward trunk lean on an instrumented treadmill while wearing instrumented insoles. The insole data were used as input to an artificial neural network that was trained to predict the Achilles tendon strain, and tibia and patellofemoral stress impulses and weighted impulses (damage proxy) as determined with musculoskeletal modeling. Accuracy was investigated using leave-one-out cross-validation and correlations. The effect of different input metrics was also assessed.

RESULTS

The neural network predicted tissue loading with overall relative percentage errors of 1.95 ± 8.40%, -7.37 ± 6.41%, and -12.8 ± 9.44% for the patellofemoral joint, tibia, and Achilles tendon impulse, respectively. The accuracy significantly changed with altered running speed, slope, or step frequency. Mean (95% confidence interval) within-individual correlations between modeled and predicted impulses across conditions were generally nearly perfect, being 0.92 (0.89 to 0.94), 0.95 (0.93 to 0.96), and 0.95 (0.94 to 0.96) for the patellofemoral, tibial, and Achilles tendon stress/strain impulses, respectively.

CONCLUSIONS

This study shows that commercially available instrumented insoles can predict loading at common running injury locations with variable absolute but (very) high relative accuracy. The absolute error was lower than the methods that measure only the step count or assume a constant load per speed or slope. This developed model may allow for quantification of in-field tissue loading and real-time tissue loading-based feedback to reduce injury risk.

Physical Activity Levels in Persons With Patellofemoral Pain: A Systematic Review and Meta-analysis

CONTEXT

Pain and symptoms of patellofemoral pain (PFP) are often exacerbated during daily activities, which may result in reduced overall physical activity levels.

OBJECTIVE

To summarize the evidence for physical activity levels among persons with PFP compared with pain-free controls.

DATA SOURCES

PubMed, Embase, CINHAL, Cochrane Library, and SPORTDiscus were searched from January 1, 2000 to February 22, 2024.

STUDY SELECTION

Peer-reviewed studies published in English that measured physical activity subjectively or objectively in persons with PFP and pain-free controls.

STUDY DESIGN

Systematic review with meta-analysis.

LEVEL OF EVIDENCE

Level 1.

DATA EXTRACTION

Standardized mean difference (SMD) with 95% CI are reported based on Hedges' g effect sizes.

RESULTS

From 23,745 records, 41 studies met the eligibility criteria. There was high-to-moderate-certainty evidence that persons with PFP reported higher physical activity levels compared with pain-free controls using the International Physical Activity Questionnaire (SMD, 0.27; 95% CI 0.03, 0.51), whereas lower physical activity levels compared with pain-free controls using the Tegner Activity Scale (SMD, -0.31; 95% CI -0.57, -0.04). There was low-to-moderate-certainty evidence that there was no group difference in physical activity levels using the Baecke Physical Activity Questionnaire (SMD, 0.17; 95% CI -0.09, 0.44) or self-reported sports participation duration (SMD, -0.46; 95% CI -0.98, 0.05). There was high-certainty evidence that runners with PFP reported shorter running distances compared with pain-free runners (SMD, -0.36, 95% CI -0.57, -0.14). No data pooling was possible for objectively measured physical activity levels due to device heterogeneity (ie, different algorithms used to quantify the intensity of physical activity).

CONCLUSION

Self-reported physical activity levels among persons with PFP were inconsistent depending on the physical activity measurement tool used or which specific physical activity was measured. Clinicians should integrate multiple physical activity assessment tools to determine the extent to which PFP influences physical activity levels.

TRIAL REGISTRATION

PROSPERO #CRD42022314598.

Per-step and cumulative load at three common running injury locations: The effect of speed, surface gradient, and cadence

Understanding how loading and damage on common running injury locations changes across speeds, surface gradients, and step frequencies may inform training programs and help guide progression/rehabilitation after injuries. However, research investigating tissue loading and damage in running is limited and fragmented across different studies, thereby impairing comparison between conditions and injury locations. This study examined per-step peak load and impulse, cumulative impulse, and cumulative weighted impulse (hereafter referred to as cumulative damage) on three common injury locations (patellofemoral joint, tibia, and Achilles tendon) across different speeds, surface gradients, and cadences. We also explored how cumulative damage in the different tissues changed across conditions relative to each other. Nineteen runners ran at five speeds (2.78, 3.0, 3.33, 4.0, 5.0 m s-1 ), and four gradients (-6, -3, +3, +6°), and three cadences (preferred, ±10 steps min-1 ) each at one speed. Patellofemoral, tibial, and Achilles tendon loading and damage were estimated from kinematic and kinetic data and compared between conditions using a linear mixed model. Increases in running speed increased patellofemoral cumulative damage, with nonsignificant increases for the tibia and Achilles tendon. Increases in cadence reduced damage to all tissues. Uphill running increased tibial and Achilles tendon, but decreased patellofemoral damage, while downhill running showed the reverse pattern. Per-step and cumulative loading, and cumulative loading and cumulative damage indices diverged across conditions. Moreover, changes in running speed, surface gradient, and step frequency lead to disproportional changes in relative cumulative damage on different structures. Methodological and practical implications for researchers and practitioners are discussed.

Sensor location influences the associations between IMU and motion capture measurements of impact landing in healthy male and female runners at multiple running speeds

This study investigated the relationships between inertial measurement unit (IMU) acceleration at multiple body locations and 3D motion capture impact landing measures in runners. Thirty healthy runners ran on an instrumented treadmill at five running speeds (9-17 km/h) during 3D motion capture. Axial and resultant acceleration were collected from IMUs at the distal and proximal tibia, distal femur and sacrum. Relationships between peak acceleration from each IMU location and patellofemoral joint (PFJ) peak force and loading rate, impact peak and instantaneous vertical loading rate (IVLR) were investigated using linear mixed models. Acceleration was positively related to IVLR at all lower limb locations (p < 0.01). Models predicted a 1.9-3.2 g peak acceleration change at the tibia and distal femur, corresponding with a 10% IVLR change. Impact peak was positively related to acceleration at the distal femur only (p < 0.01). PFJ peak force was positively related to acceleration at the distal (p = 0.03) and proximal tibia (p = 0.03). PFJ loading rate was positively related to the tibia and femur acceleration in males only (p < 0.01). These findings suggest multiple IMU lower limb locations are viable for measuring peak acceleration during running as a meaningful indicator of IVLR.

Influence of foot strike patterns and cadences on patellofemoral joint stress in male runners with patellofemoral pain

OBJECTIVES

This study aimed to determine the effect of foot strike patterns and cadences in male runners with patellofemoral pain (PFP).

DESIGN

Cross-sectional study.

SETTING

Biomechanics lab.

METHODS

20 male runners with PFP were instructed to randomly complete six running conditions (three cadence conditions in rearfoot strike pattern (RFS) or forefoot strike (FFS)) under a preferred running speed.

MAIN OUTCOME MEASURES

The primary outcomes were peak knee joint and moment, and secondary outcomes were patellofemoral joint stress.

RESULTS

Running with increased cadence has a lower flexion angle (P = 0.027, η2 = 0.45), lower extension moment (P = 0.011, η2 = 0.29), lower internal rotation moment (P = 0.040, η2 = 0.17), lower patellofemoral stress (P = 0.029, η2 = 0.52) than preferred cadence. FFS running performed significantly lower flexion angle (P = 0.003, η2 = 0.39), lower extension moment (P < 0.001, η2 = 0.91), lower adduction moment (P = 0.020, η2 = 0.25) lower patellofemoral stress (P < 0.001, η2 = 0.81) than RFS running for all cadence.

CONCLUSIONS

Preliminary findings provide new perspectives for male runners with PFP to unload patellofemoral joint stress in managing PFP through the combination of the FFS pattern and increased cadence.

Cartilage thickness mismatches in patellar osteochondral allograft transplants affect local cartilage stresses

Osteochondral allograft implantation is a form of cartilage transplant in which a cylindrical graft of cartilage and subchondral bone from a donor is implanted into a patient's prepared articular defect site. No standard exists for matching the cartilage thickness of the donor and recipient. The goal of this study was to use finite element (FE) analysis to identify the effect of cartilage thickness mismatches between donor and recipient cartilage on cartilage stresses in patellar transplants. Two types of FE models were used: patient-specific 3D models and simplified 2D models. 3D models highlighted which geometric features produced high-stress regions in the patellar cartilage and provided ranges for the parameter sweeps that were conducted with 2D models. 2D models revealed that larger thickness mismatches, thicker recipient cartilage, and a donor-to-recipient cartilage thickness ratio (DRCR) < 1 led to higher stresses at the interface between the donor and recipient cartilage. A surface angle between the donor-recipient cartilage interface and cartilage surface normal near the graft boundary increased stresses when DRCR > 1, with the largest increase observed for an angle of 15°. A surface angle decreased stresses when DRCR < 1. Clinical Significance: This study highlights a potential mechanism to explain the high rates of failure of patellar OCAs. Additionally, the relationship between geometric features and stresses explored in this study led to a hypothetical scoring system that indicates which transplanted patellar grafts may have a higher risk of failure.

Injury and performance related biomechanical differences between recreational and collegiate runners

Introduction

Running related injuries (RRI) are common, but factors contributing to running performance and RRIs are not commonly compared between different types of runners.

Methods

We compared running biomechanics previously linked to RRIs and performance between 27 recreational and 35 collegiate runners. Participants completed 5 overground running trials with their dominant limb striking a force plate, while outfitted with standardised footwear and 3-dimensional motion capture markers.

Results

Post hoc comparisons revealed recreational runners had a larger vertical loading rate (194.5 vs. 111.5 BW/s, p < 0.001) and shank angle (6.80 vs. 2.09, p < 0.001) compared with the collegiate runners who demonstrated greater vertical impulse (0.349 vs. 0.233 BWs, p < 0.001), negative impulse (-0.022 vs. -0.013 BWs, p < 0.001), positive impulse (0.024 vs. 0.014 BWs, p < 0.001), and propulsive force (0.390 vs. 0.333 BW, p = 0.002). Adjusted for speed, collegiate runners demonstrated greater total support moment (TSM), plantar flexor moment, knee extensor moment, hip extensor moment, and had greater proportional plantar flexor moment contribution and less knee extensor moment contribution to the TSM compared with recreational runners. Unadjusted for speed, collegiate runners compared with recreational had greater TSM and plantar flexor moment but similar joint contributions to the TSM.

Discussion

Greater ankle joint contribution may be more efficient and allow for greater capacity to increase speed. Improving plantarflexor function during running provides a strategy to improve running speed among recreational runners. Moreover, differences in joint kinetics and ground reaction force characteristics suggests that recreational and collegiate runners may experience different types of RRI.

Case study: The influence of Achilles tendon rupture on knee joint stress during counter-movement jump - Combining musculoskeletal modeling and finite element analysis

BACKGROUND

Presently, the current research concerning Achilles tendon rupture repair (ATR) is predominantly centered on the ankle joint, with a paucity of evidence regarding its impact on the knee joint. ATR has the potential to significantly impede athletic performance and increase tibiofemoral contact forces in athletes. The purpose of this study was to prognosticate the distribution of stress within the knee joint during a countermovement jump through the use of a simulation method that amalgamated a musculoskeletal model of a patient who underwent Achilles tendon rupture repair with a finite element model of the knee joint.

METHODS

A male elite badminton player who had suffered an acute Achilles tendon rupture in his right leg one year prior was selected as our study subject. In order to analyze his biomechanical data, we employed both the OpenSim musculoskeletal model and finite element model to compute various parameters such as joint angles, joint moments, joint contact forces, and the distribution of knee joint stress.

RESULTS

During the jumping phase, a significantly lower knee extension angle (p < 0.001), ankle dorsiflexion angle (p = 0.002), peak vertical ground reaction force (p < 0.001), and peak tibiofemoral contact force (p = 0.009) were observed on the injured side than on the uninjured side. During the landing phase, the ankle range of motion (ROM) was significantly lower on the injured side than on the uninjured side (p = 0.009), and higher peak vertical ground reaction forces were observed (p = 0.012). Additionally, it is logical that an injured person will put higher load on the uninjured limb, but the finite element analysis indicated that the stresses on the injured side of medial meniscus and medial cartilage were significantly greater than the uninjured side.

CONCLUSIONS

An Achilles tendon rupture can limit ankle range of motion and lead to greater joint stress on the affected area during countermovement jumps, especially during the landing phase. This increased joint stress may also transfer more stress to the soft tissues of the medial knee, thereby increasing the risk of knee injury. It is worth noting that this study only involves the average knee flexion angle and load after ATR in one athlete. Caution should be exercised when applying the conclusions, and in the future, more participants should be recruited to establish personalized knee finite element models to validate the results.

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.

Persons with Patellar Tendinopathy Exhibit Greater Patellar Tendon Stress during a Single-Leg Landing Task

PURPOSE

This study aimed to compare peak maximum principal stress in the patellar tendon between persons with and without patellar tendinopathy during a simulated single-leg landing task. A secondary purpose was to determine the biomechanical predictor(s) of peak maximum principal stress in the patellar tendon.

METHODS

Using finite element (FE) modeling, patellar tendon stress profiles of 28 individuals (14 with patellar tendinopathy and 14 pain-free controls) were created at the time of the peak knee extensor moment during single-leg landing. Input parameters to the FE model included subject-specific knee joint geometry and kinematics, and quadriceps muscle forces. Independent t -tests were used to compare the peak maximum principal stress in the patellar tendon and biomechanical variables used as input variables to the FE model (knee flexion, knee rotation in the frontal and transverse planes and the peak knee extensor moment) between groups. A stepwise regression model was used to determine the biomechanical predictor(s) of peak maximum principal stress in the patellar tendon for both groups combined.

RESULTS

Compared with the control group, persons with patellar tendinopathy exhibited greater peak maximum principal stress in the patellar tendon (77.4 ± 25.0 vs 60.6 ± 13.6 MPa, P = 0.04) and greater tibiofemoral joint internal rotation (4.6° ± 4.6° vs 1.1° ± 4.2°, P = 0.04). Transverse plane rotation of the tibiofemoral joint was the best predictor of peak maximum principal stress in the patellar tendon ( r = 0.51, P = 0.01).

CONCLUSIONS

Persons with patellar tendinopathy exhibit greater peak patellar tendon stress compared with pain-free individuals during single-leg landing. The magnitude of peak patellar tendon stress seems to be influenced by the amount of tibiofemoral rotation in the transverse plane.

Patellofemoral joint load and knee abduction/adduction moment are sensitive to variations in femoral version and individual muscle forces

Torsional profiles of the lower limbs, such as femoral anteversion, can dictate gait and mobility, joint biomechanics and pain, and functional impairment. It currently remains unclear how the interactions between femoral anteversion, kinematics, and muscle activity patterns contribute to joint biomechanics and thus conditions such as knee pain. This study presents a computational modeling approach to investigating the interactions between femoral anteversion, muscle forces, and knee joint loads. We employed an optimal control approach to produce actuator and muscle-driven simulations of the stance phase of gait for femoral anteversion angles ranging from -8° (retroversion) to 52° (anteversion) with a typically developing baseline of 12° of anteversion and implemented a Monte Carlo analysis for variations in lower limb muscle forces. While total patellofemoral joint load decreased with increasing femoral anteversion, patellofemoral joint load alignment worsened, and knee abduction/adduction magnitude increased with both positive and negative changes in femoral anteversion (p < 0.001). The rectus femoris muscle was found to greatly influence patellofemoral joint loads across all femoral anteversion alignments (R > 0.8, p < 0.001), and the medial gastrocnemius was found to greatly influence knee abduction/adduction moments for the extreme version cases (R > 0.74, p < 0.001). Along with the vastus lateralis, which decreased with increasing femoral anteversion (R = 0.89, p < 0.001), these muscles are prime candidates for future experimental and clinical efforts to address joint pain in individuals with extreme femoral version. These findings, along with future modeling efforts, could help clinicians better design treatment strategies for knee joint pain in populations with extreme femoral anteversion or retroversion.

Kinematic and Kinetic Gait Characteristics in People with Patellofemoral Pain: A Systematic Review and Meta-analysis

BACKGROUND

Patellofemoral pain (PFP) is a prevalent knee condition with many proposed biomechanically orientated etiological factors and treatments.

OBJECTIVE

We aimed to systematically review and synthesize the evidence for biomechanical variables (spatiotemporal, kinematic, kinetic) during walking and running in people with PFP compared with pain-free controls, and determine if biomechanical variables contribute to the development of PFP.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

We searched Medline, CINAHL, SPORTDiscus, Embase, and Web of Science from inception to October 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

All study designs (prospective, case-control [± interventional component, provided pre-intervention data were reported for both groups], cross-sectional) comparing spatiotemporal, kinematic, and/or kinetic variables during walking and/or running between people with and without PFP.

RESULTS

We identified 55 studies involving 1300 people with PFP and 1393 pain-free controls. Overall pooled analysis identified that people with PFP had slower gait velocity [moderate evidence, standardized mean difference (SMD) - 0.50, 95% confidence interval (CI) - 0.72, - 0.27], lower cadence (limited evidence, SMD - 0.43, 95% CI - 0.74, - 0.12), and shorter stride length (limited evidence, SMD - 0.46, 95% CI - 0.80, - 0.12). People with PFP also had greater peak contralateral pelvic drop (moderate evidence, SMD - 0.46, 95% CI - 0.90, - 0.03), smaller peak knee flexion angles (moderate evidence, SMD - 0.30, 95% CI - 0.52, - 0.08), and smaller peak knee extension moments (limited evidence, SMD - 0.41, 95% CI - 0.75, - 0.07) compared with controls. Females with PFP had greater peak hip flexion (moderate evidence, SMD 0.83, 95% CI 0.30, 1.36) and rearfoot eversion (limited evidence, SMD 0.59, 95% CI 0.03, 1.14) angles compared to pain-free females. No significant between-group differences were identified for all other biomechanical variables. Data pooling was not possible for prospective studies.

CONCLUSION

A limited number of biomechanical differences exist when comparing people with and without PFP, mostly characterized by small-to-moderate effect sizes. People with PFP ambulate slower, with lower cadence and a shortened stride length, greater contralateral pelvic drop, and lower knee flexion angles and knee extension moments. It is unclear whether these features are present prior to PFP onset or occur as pain-compensatory movement strategies given the lack of prospective data.

TRIAL REGISTRATION

PROSPERO # CRD42019080241.

An Updated Model Does Not Reveal Sex Differences in Patellofemoral Joint Stress during Running

Background

Structure-specific loading may have implications in understanding the mechanisms of running related injury. As females demonstrate a prevalence of patellofemoral pain twice that of males, this may indicate differences in patellofemoral loads between males and females. Previous works investigating differences in patellofemoral joint stress have shown conflicting results, but the models employed have not used estimates of muscle forces or sex specific contact areas.

Hypothesis/Purpose

The aim of this study was to examine sex differences in patellofemoral joint stress using an updated model to include estimates of quadriceps muscle force and sex-specific patellofemoral contact area.

Study Design

Descriptive Laboratory Study.

Methods

Forty-five healthy recreational runners ran at a controlled speed down a 20-meter runway. Kinetic and kinematic data were utilized to estimate muscle forces using static optimization. Quadriceps muscle force was utilized with sex-specific patellofemoral joint contact area in a two-dimensional patellofemoral joint model to estimate patellofemoral joint stress. Multivariate tests were utilized to detect sex differences in patellofemoral loading and hip and knee kinematics.

Results

No differences were found between sexes in measures of patellofemoral loading or quadriceps force. Females displayed a reduced knee extension moment and greater hip adduction and internal rotation than males.

Conclusion

The inclusion of static optimization to estimate quadriceps muscle force and sex-specific contact area of the patellofemoral joint did not reveal sex differences in patellofemoral joint stress, but differences in non-sagittal plane hip motion were detected. Therefore, two-dimensional patellofemoral models may not fully characterize differences in patellofemoral joint stress between males and females. Three-dimensional patellofemoral models may be necessary to determine if sex differences in patellofemoral joint stress exist.

Level of Evidence

3b.

Reversing the Mismatch With Forefoot Striking to Reduce Running Injuries

Recent studies have suggested that 95% of modern runners land with a rearfoot strike (RFS) pattern. However, we hypothesize that running with an RFS pattern is indicative of an evolutionary mismatch that can lead to musculoskeletal injury. This perspective is predicated on the notion that our ancestors evolved to run barefoot and primarily with a forefoot strike (FFS) pattern. We contend that structures of the foot and ankle are optimized for forefoot striking which likely led to this pattern in our barefoot state. We propose that the evolutionary mismatch today has been driven by modern footwear that has altered our footstrike pattern. In this paper, we review the differences in foot and ankle function during both a RFS and FFS running pattern. This is followed by a discussion of the interaction of footstrike and footwear on running mechanics. We present evidence supporting the benefits of forefoot striking with respect to common running injuries such as anterior compartment syndrome and patellofemoral pain syndrome. We review the importance of a gradual shift to FFS running to reduce transition-related injuries. In sum, we will make an evidence-based argument for the use of minimal footwear with a FFS pattern to optimize foot strength and function, minimize ground reaction force impacts and reduce injury risk.

Running Injury Paradigms and Their Influence on Footwear Design Features and Runner Assessment Methods: A Focused Review to Advance Evidence-Based Practice for Running Medicine Clinicians

Many runners seek health professional advice regarding footwear recommendations to reduce injury risk. Unfortunately, many clinicians, as well as runners, have ideas about how to select running footwear that are not scientifically supported. This is likely because much of the research on running footwear has not been highly accessible outside of the technical footwear research circle. Therefore, the purpose of this narrative review is to update clinical readers on the state of the science for assessing runners and recommending running footwear that facilitate the goals of the runner. We begin with a review of basic footwear construction and the features thought to influence biomechanics relevant to the running medicine practitioner. Subsequently, we review the four main paradigms that have driven footwear design and recommendation with respect to injury risk reduction: Pronation Control, Impact Force Modification, Habitual Joint (Motion) Path, and Comfort Filter. We find that evidence in support of any paradigm is generally limited. In the absence of a clearly supported paradigm, we propose that in general clinicians should recommend footwear that is lightweight, comfortable, and has minimal pronation control technology. We further encourage clinicians to arm themselves with the basic understanding of the known effects of specific footwear features on biomechanics in order to better recommend footwear on a patient-by-patient basis.

Offloading Effects on Impact Forces and Patellofemoral Joint Loading During Running in Females

BACKGROUND

Structure-specific loading is being increasingly recognized as playing a role in running related injuries. The use of interventions targeted at reducing patellofemoral joint loads have shown effectiveness in reducing symptoms of patellofemoral pain. Use of bodyweight support (BWS) has the potential to reduce loading on the patellofemoral joint during running to augment rehabilitation efforts.

RESEARCH QUESTION

How is patellofemoral joint loading different when using a harness-based BWS system during running?

METHODS

Twenty-five healthy females free from lower extremity injury were included. Participants completed four running trials on an instrumented treadmill with varying amounts of BWS using a commercially available harness system. Kinematic data from a 3D motion capture system and kinetic data from the treadmill were combined in a computer model to estimate measures of patellofemoral joint loading, knee kinematics, ground reaction force, and stride frequency.

RESULTS

Peak patellofemoral joint stress and time-integral were reduced when running under BWS conditions compared to control conditions. Incremental decreases in patellofemoral loading were not observed with incremental increases in BWS. Peak knee flexion angle was reduced in all BWS conditions compared to control but was not different between BWS conditions. Knee flexion excursion was reduced in only the high BWS condition. Peak ground reaction force and stride frequency incrementally decreased with increased amounts of BWS.

SIGNIFICANCE

Harness-based BWS systems may provide a simple means to reduce patellofemoral joint loading to assist in rehabilitation efforts, such as addressing patellofemoral pain.

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.

Running-Related Biomechanical Risk Factors for Overuse Injuries in Distance Runners: A Systematic Review Considering Injury Specificity and the Potentials for Future Research

BACKGROUND

Running overuse injuries (ROIs) occur within a complex, partly injury-specific interplay between training loads and extrinsic and intrinsic risk factors. Biomechanical risk factors (BRFs) are related to the individual running style. While BRFs have been reviewed regarding general ROI risk, no systematic review has addressed BRFs for specific ROIs using a standardized methodology.

OBJECTIVE

To identify and evaluate the evidence for the most relevant BRFs for ROIs determined during running and to suggest future research directions.

DESIGN

Systematic review considering prospective and retrospective studies. (PROSPERO_ID: 236,832).

DATA SOURCES

PubMed. Connected Papers. The search was performed in February 2021.

ELIGIBILITY CRITERIA

English language. Studies on participants whose primary sport is running addressing the risk for the seven most common ROIs and at least one kinematic, kinetic (including pressure measurements), or electromyographic BRF. A BRF needed to be identified in at least one prospective or two independent retrospective studies. BRFs needed to be determined during running.

RESULTS

Sixty-six articles fulfilled our eligibility criteria. Levels of evidence for specific ROIs ranged from conflicting to moderate evidence. Running populations and methods applied varied considerably between studies. While some BRFs appeared for several ROIs, most BRFs were specific for a particular ROI. Most BRFs derived from lower-extremity joint kinematics and kinetics were located in the frontal and transverse planes of motion. Further, plantar pressure, vertical ground reaction force loading rate and free moment-related parameters were identified as kinetic BRFs.

CONCLUSION

This study offers a comprehensive overview of BRFs for the most common ROIs, which might serve as a starting point to develop ROI-specific risk profiles of individual runners. We identified limited evidence for most ROI-specific risk factors, highlighting the need for performing further high-quality studies in the future. However, consensus on data collection standards (including the quantification of workload and stress tolerance variables and the reporting of injuries) is warranted.

Relationship between vastus medialis Hoffmann reflex excitability and knee extension biomechanics during different tasks in women with patellofemoral pain

BACKGROUND

Impaired knee extension biomechanics and spinal excitability have been reported in women with patellofemoral pain, but their relationship has not been explored. A significant relationship between them could indicate the need for investigating the potential benefits of disinhibitory interventions for women with patellofemoral pain. Thus, this study aimed to investigate the relationship between vastus medialis Hoffmann reflex and (1) maximal isometric, concentric and eccentric knee extensor strength and rate of torque development; (2) knee extensor torque steadiness; and (3) knee extensor moment during functional tasks; in women with patellofemoral pain.

METHODS

Spinal excitability of twenty-four participants was assessed by the amplitude of maximal vastus medialis Hoffmann reflex. Knee extensor strength, rate of torque development and torque steadiness were assessed using an isokinetic dynamometer. Knee extensor moment during step-down and stair descent tasks were obtained using a three-dimensional motion analysis system.

FINDINGS

A moderate negative relationship was found between vastus medialis Hoffmann reflex and knee extensor torque steadiness (r = -0.35; p = 0.05); whereas a moderate positive relationship was found with maximal isometric knee extensor strength (r = 0.37; p = 0.044). No significant relationships were found between vastus medialis Hoffmann reflex and the other variables.

INTERPRETATION

Our findings provide insight on the relationship between spinal excitability and neuromuscular control of maximal and submaximal isometric torque production in women with patellofemoral pain. Conversely, spinal excitability does not seem to be related with dynamic torques and moments of the knee extensors in women with patellofemoral pain.

The effect of speed on Achilles tendon forces and patellofemoral joint stresses in high-performing endurance runners

Achilles tendinopathy and patellofemoral pain are common running injuries associated with increased Achilles tendon (AT) forces and patellofemoral joint (PFJ) stresses. This study examined AT forces and PFJ stresses at different running speeds in high-performing endurance runners. Twenty runners ran overground at four running speeds (3.3, 3.9, 4.8, and 5.6 m/s). AT forces and PFJ stresses were estimated from kinematic and kinetic data. Repeated measures ANOVA with partial eta squared effect sizes was conducted to assess differences between running speeds. Increased peak AT forces (19.5%; p < 0.001) and loading rates (57.3%; p < 0.001) from 3.3 m/s to 5.6 m/s were observed. Cumulative AT loading was greater in the faster speeds compared to the slower speeds. Faster running speeds resulted in increased peak plantar flexor moments, increased peak plantar flexion angles, and a more flexed knee and an anterior center of pressure position at touchdown. Peak PFJ stress was lower in the slowest speed (3.3 m/s) compared to the faster running speeds (3.9-5.6 m/s; p = 0.005). PFJ stress loading rate significantly increased (43.6%; p < 0.001). Greater AT loading observed could be associated with strategies such as increased plantar flexor moments and altered lower body position at touchdown which are commonly employed to generate greater ground contact forces. Greater AT and PFJ loading rates were likely due to shorter ground contact times and therefore less time available to reach the peak. Running at faster speeds could increase the risk of developing Achilles tendinopathy and patellofemoral pain or limit recovery from these injuries without sufficient recovery.

Biomechanics Differ for Individuals With Similar Self-Reported Characteristics of Patellofemoral Pain During a High-Demand Multiplanar Movement Task

CONTEXT

Patellofemoral pain (PFP) is often categorized by researchers and clinicians using subjective self-reported PFP characteristics; however, this practice might mask important differences in movement biomechanics between PFP patients.

OBJECTIVE

To determine whether biomechanical differences exist during a high-demand multiplanar movement task for PFP patients with similar self-reported PFP characteristics but different quadriceps activation levels.

DESIGN

Cross-sectional design.

SETTING

Biomechanics laboratory.

PARTICIPANTS

A total of 15 quadriceps deficient and 15 quadriceps functional (QF) PFP patients with similar self-reported PFP characteristics.

INTERVENTION

In total, 5 trials of a high-demand multiplanar land, cut, and jump movement task were performed.

MAIN OUTCOME MEASURES

Biomechanics were compared at each percentile of the ground contact phase of the movement task (α = .05) between the quadriceps deficient and QF groups. Biomechanical variables included (1) whole-body center of mass, trunk, hip, knee, and ankle kinematics; (2) hip, knee, and ankle kinetics; and (3) ground reaction forces.

RESULTS

The QF patients exhibited increased ground reaction force, joint torque, and movement, relative to the quadriceps deficient patients. The QF patients exhibited: (1) up to 90, 60, and 35 N more vertical, posterior, and medial ground reaction force at various times of the ground contact phase; (2) up to 4° more knee flexion during ground contact and up to 4° more plantarflexion and hip extension during the latter parts of ground contact; and (3) up to 26, 21, and 48 N·m more plantarflexion, knee extension, and hip extension torque, respectively, at various times of ground contact.

CONCLUSIONS

PFP patients with similar self-reported PFP characteristics exhibit different movement biomechanics, and these differences depend upon quadriceps activation levels. These differences are important because movement biomechanics affect injury risk and athletic performance. In addition, these biomechanical differences indicate that different therapeutic interventions may be needed for PFP patients with similar self-reported PFP characteristics.

Combining advanced computational and imaging techniques as a quantitative tool to estimate patellofemoral joint stress during downhill gait: A feasibility study

BACKGROUND

The onset and progression of patellofemoral osteoarthritis (OA) has been linked to alterations in cartilage stress-a potential precursor to pain and subsequent cartilage degradation. A lack in quantitative tools for objectively evaluating patellofemoral joint contact stress limits our understanding of pathomechanics associated with OA.

RESEARCH QUESTION

Could computational modeling and biplane fluoroscopy techniques be used to discriminate in-vivo, subject-specific patellofemoral stress profiles in individuals with and without patellofemoral OA?

METHODS

The current study employed a discrete element modeling framework driven by in-vivo, subject-specific kinematics during downhill gait to discriminate unique patellofemoral stress profiles in individuals with patellofemoral OA (n = 5) as compared to older individuals without OA (n = 6). All participants underwent biplane fluoroscopy kinematic tracking while walking on a declined instrumented treadmill. Subject-specific kinematics were combined with high resolution geometrical models to estimate patellofemoral joint contact stress during 0%, 25 %, 50 %, 75 % and 100 % of the loading response phase of downhill gait.

RESULTS

Individuals with patellofemoral OA demonstrated earlier increases in patellofemoral stress in the lateral patellofemoral compartment during loading response as compared to OA-free controls (P = 0.021). Overall, both groups exhibited increased patellofemoral contact stress early in the loading response phase of gait as compared to the end of loading response. Results from this study show increased stress profiles in individuals with patellofemoral OA, indicating increasing joint loading in early phases of gait.

SIGNIFICANCE

This modeling framework-combining arthrokinematics with discrete element models-can objectively estimate changes in patellofemoral joint stress, with potential applications to evaluate outcomes from various treatment programs, including surgical and non-surgical rehabilitation treatments.

Effect of gait retraining on segment coordination and joint variability in individuals with patellofemoral pain

BACKGROUND

Gait retraining is advocated for the management of patellofemoral pain. This case series examined changes in lower limb variability following 6-weeks of gait retraining in individuals with patellofemoral pain.

METHODS

Six runners with patellofemoral pain completed a 6-week physiotherapist-guided gait retraining program using minimalist footwear and increased cadence. Approximate entropy joint variability and segment coordination variability were calculated across the entire gait cycle during running at baseline, 6 and 12 weeks and compared using repeated measures analysis of variance and the standardised mean difference (SMD).

FINDINGS

Compared to baseline, there were large increases in hip joint transverse plane kinematic variability at 6 (SMD = 1.7) and 12 weeks (SMD = 1.3). Moderate increases in hip joint frontal plane and knee joint sagittal plane kinematic variability were also observed at 6 (SMD = 1.1 & 0.96) and 12 weeks (SMD = 1.1 & 0.89). Knee joint frontal plane and hip joint transverse plane kinetic variability demonstrated large increases from baseline at 6 (SMD = 1.3 & 0.9) and 12 weeks (SMD = 0.9 & 1.0). There was no main effect of time for segment coordination variability. All participants had clinically meaningful improvements in pain (visual analogue change score > 20 mm).

INTERPRETATION

Gait retraining increased joint kinematic and kinetic variability in those with patellofemoral pain and these changes persisted over 12 weeks. Increased variability was observed in joint kinematics and kinetics known to influence patellofemoral joint stress, which may vary patellofemoral joint loading patterns and partly explain the clinical effect.

Achilles tendon elongation after acute rupture: is it a problem? A systematic review

PURPOSE

Rupture of the Achilles tendon (AT) is a common injury. Strength deficits may persist over the long term, possibly owing to elongation of the tendon or inferior mechanical properties. This study aimed to provide a systematic review of the literature on the prevalence and consequences of tendon elongation in patients after acute AT rupture treatment. It was hypothesized that an elongated tendon would be associated with a worse clinical outcome.

METHODS

The databases for MEDLINE, CENTRAL and Web of Science were searched. Clinical studies related to AT rupture reporting tendon elongation and clinical or functional outcomes, with a minimum follow-up of 6 months, were eligible for inclusion. Only studies testing for statistical correlations (SCs) between AT elongation and other outcomes were eligible, with the exception of biomechanical studies in which statistically significant AT elongation was found to be a generalized finding in the study group. For these studies to be eligible, the study group had to be compared with a healthy control group, or the injured limb compared with the uninjured limb, regarding biomechanical parameters.

RESULTS

Twenty-eight papers were selected for inclusion. Mean AT elongation measured with imaging techniques ranged from 0.15 to 3.1 cm (n = 17). Ten studies investigated SCs with Patient Reported Outcome Measures (PROMs), in which two found SCs with tendon elongation. Five studies reported strength and power evaluations and their correlation with AT elongation, with two having found SCs between decreased strength and tendon elongation. In ten studies reporting data on biomechanical tests, nine found influence of tendon elongation. In this group, four out of five studies found SCs with biomechanical parameters.

CONCLUSION

Fair evidence of the influence of tendon elongation in biomechanical parameters was found. In a general population, evidence of a detrimental effect of tendon elongation on PROMs or functional strength at follow-up was not found in this review.

LEVEL OF EVIDENCE

Level IV.

Patellar Malalignment Is Associated With Patellofemoral Lesions and Cartilage Relaxation Times After Hamstring Autograft Anterior Cruciate Ligament Reconstruction

BACKGROUND

There is growing evidence suggesting a link between patellofemoral joint (PFJ) osteoarthritis in anterior cruciate ligament (ACL)-reconstructed knees and altered joint alignment.

PURPOSE

To determine whether patellar alignment differs between participants with and without ACL reconstruction (ACLR) and to identify possible associations between patellar alignment and PFJ osteoarthritis features over 3 years.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 37 participants with ACLR (sex, 23 male; mean ± SD age, 28.1 ± 7.4 years) and 20 healthy controls (13 male; 30.4 ± 4.8 years) participated. Patients underwent magnetic resonance imaging: (1) sagittal T2-weighted fat-saturated fast spin echo images to calculate patellar alignment, (2) sagittal 3-dimensional intermediate-weighted fast spin echo Cube sequence for clinical morphological grading (modified Whole-Organ Magnetic Resonance Imaging Score [WORMS]), and (3) sagittal combined T_1ρ/T₂ mapping sequence for performing voxel-based relaxometry. Patellar alignment of the ACLR knees were assessed at 6 months (baseline). One-way analysis of variance was used to compare patellar alignment among the ACLR (at 6 months), contralateral, and control knees. Within the ACLR group, a logistic regression model was used to identify if patellar alignment measures at baseline were risk factors for worsening of PFJ structural changes over 3 years. Statistical parametric mapping was used to evaluate the longitudinal associations between patellar alignment and cartilage relaxation times at 3 years.

RESULTS

When compared with control knees, ACLR knees exhibited a laterally and anteriorly displaced patella (P = .045 and P = .041), less flexion (P = .031), and less lateral spin (P = .012). Furthermore, excessive lateral displacement was a significant predictor of worsening of WORMS (P = .050). Lateral displacement was positively correlated with increased T_1ρ and T₂ in the patellar and trochlear cartilage at 3 years. Patellar lateral spin revealed similar negative findings.

CONCLUSION

Participants with ACLR exhibited a laterally and anteriorly displaced patella, less flexion, and less lateral spin when compared with healthy controls. Excessive patellar lateral displacement was the strongest predictor to the development of PFJ osteoarthritis features longitudinally.

Patellofemoral Mechanics: a Review of Pathomechanics and Research Approaches

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Twelve-Week Gait Retraining Reduced Patellofemoral Joint Stress during Running in Male Recreational Runners

Purpose

To explore the changes in knee sagittal angle and moment and patellofemoral joint (PFJ) force and stress before and after 12-week gait retraining.

Methods

A total of 30 healthy male recreational runners were randomized into a control group (n = 15) who ran in their original strike pattern using minimalist shoes or experimental group (n = 15) who ran in a forefoot strike pattern using minimalist shoes during the 12-week gait retraining. The kinematic and kinetic data of the dominant leg of the participants during the 12 km/h running were collected by 3D motion capture systems and 3D force platforms. Besides, the biomechanical property of the PFJ was calculated on the basis of the joint force model and the regression equation of the contact area.

Results

After the 12-week gait retraining, 78% of the rearfoot strikers turned into forefoot strikers. Peak knee extension moment and peak PFJ stress decreased by 13.8% and 13.3% without altering the running speed, respectively. Meanwhile, no changes in maximum knee flexion angle/extension moment and PFJ force/stress were observed for the control group.

Conclusion

The 12-week gait retraining effectively reduced the PFJ stress, thereby providing a potential means of reducing the risk of patellofemoral pain syndrome while running.

Gait Retraining as an Intervention for Patellofemoral Pain

PURPOSE OF REVIEW

Movement retraining in rehabilitation is the process by which a motor program is changed with the overall goal of reducing pain or injury risk. Movement retraining is an important component of interventions to address patellofemoral pain. The purpose of this paper is to review the methods and results of current retraining studies that are aimed at reducing symptoms of patellofemoral pain.

RECENT FINDINGS

The majority of studies reviewed demonstrated some improvement in patellofemoral pain symptoms and overall function. However, the degree of improvement as well as the persistence of improvement over time varied between studies. The greatest pain reduction and persistent changes were noted in those studies that incorporated a faded feedback design including between 8 and 18 sessions over 2-6 weeks, typically 3-4 sessions per week. Additionally, dosage in these studies increased to 30-45 min during later sessions, resulting in 177-196 total minutes of retraining. In contrast, pain reductions and persistence of changes were the least in studies where overall retraining volume was low and feedback was either absent or continual. Faulty movement patterns have been associated with patellofemoral pain. Studies have shown that strengthening alone does not alter these patterns, and that addressing the motor program is needed to effect these changes. Based upon the studies reviewed here, retraining faulty patterns, when present, appears to play a significant role in addressing patellofemoral pain. Therefore, movement retraining, while adhering to basic motor control principles, should be part of a therapist's intervention skillset when treating patients with PFP.

Footwear and Cadence Affect Gait Variability in Runners with Patellofemoral Pain

PURPOSE

To examine the effects of increased cadence and minimalist footwear on lower-limb variability in runners with patellofemoral pain (PFP).

METHODS

Fifteen (12 female, 3 male) runners with PFP ran on an instrumented treadmill with three-dimensional motion capture in three randomly ordered conditions: (i) standard shoe at preferred cadence, (ii) standard shoe +10% cadence, and (iii) minimalist shoe at preferred cadence. Vector coding was used to calculate coordination variability between strides for select lower-limb joint couplings. Approximate entropy was calculated to assess continuous variability for segment kinematic and kinetic data and compared between conditions using repeated-measures ANOVA. One-dimensional statistical parametric mapping repeated-measures ANOVA was performed on the coordination variability data. Cohen's d effect size was calculated for all comparisons.

RESULTS

Larger approximate entropy values (i.e., greater variability) were observed for the standard shoe +10% cadence versus the standard shoe at preferred cadence for hip flexion/extension (P < 0.001; d = 1.12), hip adduction/abduction (P < 0.001; d = 0.99) and ankle dorsiflexion/plantarflexion (P < 0.001; d = 1.37) kinematics, and knee flexion/extension moments (P < 0.001; d = 0.93). Greater variability was also observed in the minimalist shoe versus the standard shoe at preferred cadence for hip internal/external rotation moments (P < 0.001; d = 0.76), knee adduction/abduction moments (P < 0.001; d = 0.51), and knee internal/external rotation moments (P < 0.001; d = 1.02). One-dimensional statistical parametric mapping repeated-measures ANOVA revealed no significant differences in coordination variability between running conditions.

CONCLUSIONS

Greater hip and knee kinematic and kinetic variability observed with either increased cadence or minimalist footwear may be beneficial for those with PFP.

Towards a Dynamic Model of the Kangaroo Knee for Clinical Insights into Human Knee Pathology and Treatment: Establishing a Static Biomechanical Profile

There is limited understanding of how patella realignment or patellectomy to surgically manage patellofemoral pain (PFP) affects knee biomechanics. By analysing marsupials like kangaroos that lack an ossified patella, actionable biomimetic insight for the management of end-stage PFP could be gained. This study aimed to provide the foundation of a multi-stage approach, by establishing a static biomechanical profile of the kangaroo stifle that informs the inputs and factors requiring consideration for future dynamic analyses. Volumetric CT and MRI sequences were obtained for four hindlimbs from two Macropus giganteus specimens, from which three-dimensional models of the stifles were created. Two limbs were dissected to visualise the insertion points, origins and lines of action of the quadriceps muscles and the knee extensor mechanism. Static measurements were obtained from the three-dimensional models to establish the biomechanical profile. The results confirmed structural differences in the kangaroo stifle with lack of an ossified patella, a prominent tuberosity and a shorter femur, which functionally affect the mechanical advantage and the torque-generating capability of the joint. The data reported in this study can be used to inform the inputs and constraints of future comparative analyses from which important lessons can be learned for the human knee.

Osteoarthritis year in review 2018: mechanics

OBJECTIVE

To review recent biomechanics literature focused on the interactions between biomechanics and articular cartilage health, particularly focused on macro-scale and human studies.

DESIGN

A literature search was conducted in PubMed using the search terms (biomechanics AND osteoarthritis) OR (biomechanics AND cartilage) OR (mechanics AND osteoarthritis) OR (mechanics AND cartilage) for publications from April 2017 to April 2018.

RESULTS

Abstracts from the 559 articles generated from the literature search were reviewed. Due to the wide range of topics, 62 full texts with a focus on in vivo biomechanical studies were included for further discussion. Several overarching themes in the recent literature were identified and are summarized, including 1) new methods to detect early osteoarthritis (OA) development, 2) studies describing healthy and OA cartilage and biomechanics, 3) ACL injury and OA development, 4) meniscus injury and OA development, and 5) OA prevention, treatment, and management.

CONCLUSIONS

Mechanical loading is a critical factor in the maintenance of joint health. Abnormal mechanical loading can lead to the onset and progression of OA. Thus, recent studies have utilized various biomechanical models to better describe the etiology of OA development and the subsequent effects of OA on the mechanics of joint tissues and whole body biomechanics.

Tibiofemoral kinematics in the transverse and frontal planes influence the location and magnitude of peak patella cartilage stress: An investigation of runners with and without patellofemoral pain

BACKGROUND

To determine whether the location and magnitude of peak patella cartilage stress varies among runners with and without patellofemoral pain. To determine whether tibiofemoral kinematics in the frontal and transverse planes predict peak lateral and medial patella cartilage stress.

METHODS

Twelve recreational runners with patellofemoral pain and 10 pain-free controls participated. Peak patella cartilage stress was quantified using finite element models that incorporated subject-specific kinematic and kinetic data obtained during running. Chi-square analysis was used to determine whether the location of peak patella cartilage stress (medial or lateral) varied between groups. Student's t-tests were used to determine whether the magnitude of peak medial and lateral patella cartilage stress varied between groups. In addition, stepwise regression analysis was performed to determine if tibiofemoral kinematics were predictive of peak medial and lateral cartilage stress.

FINDINGS

Among all subjects, 64% exhibited peak cartilage stress on the lateral patella facet. No group differences were found for the location and magnitude of peak cartilage stress on the medial or lateral facets. Tibiofemoral rotation in the transverse plane was the best predictor of peak lateral stress (45% of the variance, r = 0.67). Tibiofemoral rotation in the transverse plane was the best predictor of peak medial stress (44% of the variance, r = -0.67), followed by tibiofemoral rotation in the frontal plane (26% of the variance, r = 0.57).

INTERPRETATIONS

The location and magnitude of peak patella cartilage stress was similar among runners with and without patellofemoral pain. Tibiofemoral kinematics in the frontal and transverse planes are predictive of cartilage stress on the medial and lateral patella facets.