Effects of step length on patellofemoral joint stress in female runners with and without patellofemoral pain

Increasing Step Rate Reduces Peak and Cumulative Insole Force in Collegiate Runners

PURPOSE

The primary goal of this study was to examine changes in peak insole force and cumulative weighted peak force (CWPF)/km with increased step rate in collegiate runners. The secondary goal was to determine whether sacral acceleration correlates with insole force when increasing step rate.

METHODS

Twelve collegiate distance runners ran 1000 m outdoors at 3.83 m·s -1 at preferred and 10% increased step rates while insole force and sacral acceleration were recorded. Cumulative weighted peak force/km was calculated from insole force based on cumulative damage models. The effects of step rate on peak insole force and CWPF·km -1 were tested using paired t tests or Wilcoxon tests. Correlation coefficients between peak axial (approximately vertical) sacral acceleration times body mass and peak insole force were calculated on cohort and individual levels.

RESULTS

Peak insole force and CWPF·km -1 decreased ( P < 0.001) with increased step rate. Peak axial sacral acceleration did not correlate with peak insole force on the cohort level ( r = 0.35, P = 0.109) but did within individuals (mean, r = 0.69-0.78; P < 0.05).

CONCLUSIONS

Increasing step rate may reduce peak vGRF and CWPF·km -1 in collegiate runners. Therefore, clinicians should consider step rate interventions to reduce peak and cumulative vGRF in this population. Individual-specific calibrations may be required to assess changes in peak vGRF in response to increasing step rate using wearable accelerometers.

The Immediate Biomechanical Effects of a Flat, Flexible School Shoe in Adolescents with Patellofemoral Pain

INTRODUCTION

Treatment options for adolescent patellofemoral pain (PFP) are limited. School footwear might be a suitable intervention to modulate patellofemoral joint (PFJ) loads in adolescents with PFP. This study examined the immediate effects of a flat, flexible school shoe compared with a traditional school shoe on knee joint kinematics and kinetics, and PFJ reaction force during walking and running in adolescents with PFP.

METHODS

A total of 28 adolescents (12 female, 16 male; mean ± SD age, 14.3 ± 1.7 yr) with PFP walked and ran on an instrumented treadmill in two randomly ordered conditions: (i) flat, flexible school shoe and (ii) traditional school shoe. Three-dimensional marker trajectory and ground reaction force data were sampled at 250 and 1000 Hz, respectively. Continuous ankle and knee joint angles and moments, PFJ reaction force, and ankle power were compared between conditions using one-dimensional statistical parametric mapping paired t -tests ( α < 0.05).

RESULTS

Walking in the flat, flexible school shoe resulted in a significant reduction in knee flexion (15%-35% of gait cycle, P < 0.001), knee extension moment (15%-40% of gait cycle, P < 0.001), and PFJ reaction force (15%-40% of gait cycle, P < 0.001) compared with the traditional school shoe. During running, knee flexion (10%-33% of gait cycle, P < 0.001), knee extension moment (15%-25% of gait cycle, P < 0.001), and PFJ reaction force (15%-25% of gait cycle, P < 0.001) were lower when wearing the flat, flexible school shoe compared with the traditional school shoe.

CONCLUSIONS

PFJ reaction force is reduced when adolescents walk and run in a flat, flexible school shoe compared with a traditional school shoe. Flat, flexible school shoes may be an effective intervention to modulate biomechanical factors related to PFP.

Relationship Between Running Biomechanics and Core Temperature Across a Competitive Road Race

BACKGROUND

Outdoor races introduce environmental stressors to runners, and core temperature changes may influence runners' movement patterns. This study assessed changes and determined relationships between sensor-derived running biomechanics and core temperature among runners across an 11.27-km road race.

HYPOTHESIS

Core temperatures would increase significantly across the race, related to changes in spatiotemporal biomechanical measures.

STUDY DESIGN

Cross-sectional cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Twenty runners (9 female, 11 male; age, 48 ± 12 years; height, 169.7 ± 9.1 cm; mass, 71.3 ± 13.4 kg) enrolled in the 2022 Falmouth Road Race were recruited. Participants used lightweight technologies (ingestible thermistors and wearable sensors) to monitor core temperature and running biomechanics throughout the race. Timestamps were used to align sensor-derived measures for 7 race segments. Observations were labeled as core temperatures generally within normal limits (<38°C) or at elevated core temperatures (≥38°C). Multivariate repeated measures analyses of variance were used to assess changes in sensor-derived measures across the race, with Bonferroni post hoc comparisons for significant findings. Pearson's r correlations were used to assess the relationship between running biomechanics and core temperature measures.

RESULTS

Eighteen participants developed hyperthermic core temperatures (39.0°C ± 0.5°C); core temperatures increased significantly across the race (P < 0.01). Kinetic measures obtained from the accelerometers, including shock, impact, and braking g, all significantly increased across the race (P < 0.01); other sensor-derived biomechanical measures did not change significantly. Core temperatures were weakly associated with biomechanics (|r range|, 0.02-0.16).

CONCLUSION

Core temperatures and kinetics increased significantly across a race, yet these outcomes were not strongly correlated. The observed kinetic changes may have been attributed to fatigue-related influences over the race.

CLINICAL RELEVANCE

Clinicians may not expect changes in biomechanical movement patterns to signal thermal responses during outdoor running in a singular event.

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.

Increasing Step Frequency Reduces Patellofemoral Joint Stress and Patellar Tendon Force Impulse More at Low Running Speed

PURPOSE

Patellofemoral pain syndrome and patellar tendinopathy are important running-related overuse injuries. This study investigated the interaction of running speed and step frequency alterations on peak and cumulative patellofemoral joint stress (PFJS) and patellar tendon force (PTF) parameters.

METHODS

Twelve healthy individuals completed an incremental running speed protocol on a treadmill at habitual, increased and decreased step frequency. Peak PFJS and PTF, peak rate of PFJS and PTF development, and PFJS and PTF impulse per kilometer (km) were calculated using musculoskeletal modeling.

RESULTS

With increasing running speed, peak PFJS ( P < 0.001) and PTF ( P < 0.001) and peak rate of PFJS ( P < 0.001) and PTF ( P < 0.001) development increased, whereas PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km decreased. While increasing step frequency by 10%, the peak PFJS ( P < 0.001) and PTF ( P < 0.001) and the PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per kilometer decreased. No significant effect of step frequency alteration was found for the peak rate of PFJS ( P = 0.008) and PTF ( P = 0.213) development. A significant interaction effect was found for PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km, suggesting that step frequency alteration was more effective at low running speed.

CONCLUSIONS

The effectiveness of step frequency alteration on PFJS and PTF impulse per km is dependent on the running speed. With regard to peak PFJS and PTF, step frequency alteration is equally effective at low and high running speeds. Step frequency alteration was not effective for peak rate of PFJS and PTF development. These findings can assist the optimization of patellofemoral joint and patellar tendon load management strategies.

Association of patellofemoral pain syndrome (PFPS) with quadratus lumborum and lower limb muscle tightness a cross-sectional study

Background

Patellofemoral pain syndrome (PFPS) is characterized by peripatellar or retro patellar pain, as a result of changes in the physical and biochemical components of the patellofemoral joint. The main contributory factor is being the excessive load on the patellofemoral joint. The change in the flexibility of lower limb muscles is one of the factors for developing PFPS.

Objective

To find the association of quadratus lumborum (QL) and lower limb muscles tightness in patients with unilateral PFPS.

Materials and methods

50 PFPS participants (21 male and 29 female) were included and assessed for muscle tightness on both affected and unaffected side. The QL, rectus femoris, hamstring, iliotibial band (ITB) and gastrocnemius tightness were measured using inch tape and mobile inclinometer. A Chi Square test and phi crammer's v criteria were used to check the association and the strength of it.

Results

A significant association was found between tightness of rectus femoris (PFPS-right Chi 19.99 p < 0.001; Phi-0.632, PFPS-left Chi-5.52 p = 0.019 and Phi- 0.332), gastrocnemius (PFPS-right Chi 8.78 p = 0.003; Phi-0.419, PFPS-left Chi- 11.41 p = 0.001; Phi- 0.478), iliotibial band (PFPS-right Chi 7.83 p = 0.005; Phi-0.396, PFPS left Chi-3.68 p = 0.055; Phi- 0.27). There was no significant association of hamstring tightness (PFPS-right Chi - 3.68 p = 0.055; Phi-0.055, PFPS left Chi-1.11 p = 0.291; Phi- 0.019) and QL (PFPS right Chi - 1.10 p = 0.293; Phi-0.293, PFPS left Chi-0.79 p = 0.372; Phi- 0.372).

Conclusion

PFPS was associated with tightness of rectus femoris, gastrocnemius, ITB and no association found between hamstring and QL muscle tightness and PFPS.

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.

Wearable technology assessing running biomechanics and prospective running-related injuries in Active Duty Soldiers

The purpose of this study was to determine if running biomechanical variables measured by wearable technology were prospectively associated with running injuries in Active Duty Soldiers. A total of 171 Soldiers wore a shoe pod that collected data on running foot strike pattern, step rate, step length and contact time for 6 weeks. Running-related injuries were determined by medical record review 12 months post-study enrollment. Differences in running biomechanics between injured and non-injured runners were compared using independent t-tests or ANCOVA for continuous variables and chi-square analyses for the association of categorical variables. Kaplan-Meier survival curves were used to estimate the time to a running-related injury. Risk factors were carried forward to estimate hazard ratios using Cox proportional hazard regression models. Forty-one participants (24%) sustained a running-related injury. Injured participants had a lower step rate than non-injured participants, but step rate did not have a significant effect on time to injury. Participants with the longest contact time were at a 2.25 times greater risk for a running-related injury; they were also relatively slower, heavier, and older. Concomitant with known demographic risk factors for injury, contact time may be an additional indicator of a running-related injury risk in Active Duty Soldiers.

Walk Smarter, Not Harder: Effects of Cadence Manipulation on Gait Biomechanics in Patients with Patellofemoral Osteoarthritis

PURPOSE

This study aimed to investigate the effect of walking cadence on knee flexion angular impulse and peak external flexion moment in patients with patellofemoral osteoarthritis (OA).

METHODS

Forty-eight patients with patellofemoral OA underwent repeated quantitative gait analyses on an instrumented treadmill using a randomized crossover design. Walking trials were conducted at a fixed gait speed, under three cadence conditions: (i) preferred cadence, (ii) +10% increased cadence, and (iii) -10% decreased cadence, completed in random order. Using a linear mixed model, we tested the association of cadence conditions with surrogate measures of patellofemoral load (primary outcome measure: knee flexion angular impulse) while controlling for body mass. We then repeated the analyses while sequentially replacing the dependent variable with secondary outcome measures.

RESULTS

Walking with increased cadence decreased (adjusted mean difference [95% confidence interval]) the knee flexion angular impulse (-0.85 N·m·s -1 [-1.52 to -0.18], d = 0.20) and peak knee flexion moment (-4.11 N·m [-7.35 to -0.86], d = 0.24), whereas walking with decreased cadence increased the knee flexion angular impulse (1.83 N·m·s -1 [1.15 to 2.49], d = 0.42) and peak knee flexion moment (3.55 N·m [0.30 to 6.78], d = 0.21). Similar decreases and increases were observed for secondary outcome measures.

CONCLUSIONS

Walking with increased cadence, while maintaining a fixed gait speed, reduces knee flexion angular impulse as well as other surrogate measures of knee loading in patients with patellofemoral OA.

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.

Running gait modifications can lead to immediate reductions in patellofemoral pain

Gait modifications are commonly advocated to decrease knee forces and pain in runners with patellofemoral pain (PFP). However, it remains unknown if clinicians can expect immediate effects on symptoms. Our objectives were (1) to compare the immediate effects of gait modifications on pain and kinetics of runners with PFP; (2) to compare kinetic changes in responders and non-responders; and (3) to compare the effects between rearfoot strikers (RFS) and non-RFS. Sixty-eight runners with PFP (42 women, 26 men) ran normally on a treadmill before testing six modifications: 1- increase step rate by 10%; 2- 180 steps per minute; 3- decrease step rate by 10%; 4- forefoot striking; 5- heel striking; 6- running softer. Overall, there were more responders (pain decreased ≥1/10 compared with normal gait) during forefoot striking and increasing step rate by 10% (both 35%). Responders showed greater reductions in peak patellofemoral joint force than non-responders during all conditions except heel striking. When compared with non-RFS, RFS reduced peak patellofemoral joint force in a significant manner (P < 0.001) during forefoot striking (partial η ² = 0.452) and running softer (partial η ² = 0.302). Increasing step rate by 10% reduced peak patellofemoral joint force in both RFS and non-RFS. Forty-two percent of symptomatic runners reported immediate reductions in pain during ≥1 modification, and 28% had reduced pain during ≥3 modifications. Gait modifications leading to decreased patellofemoral joint forces may be associated with immediate pain reductions in runners with PFP. Other mechanisms may be involved, given that some runners reported decreased symptoms regardless of kinetic changes.

Trunk Biomechanics in Individuals with Knee Disorders: A Systematic Review with Evidence Gap Map and Meta-analysis

BACKGROUND

The trunk is the foundation for transfer and dissipation of forces throughout the lower extremity kinetic chain. Individuals with knee disorders may employ trunk biomechanical adaptations to accommodate forces at the knee or compensate for muscle weakness. This systematic review aimed to synthesize the literature comparing trunk biomechanics between individuals with knee disorders and injury-free controls.

METHODS

Five databases were searched from inception to January 2022. Observational studies comparing trunk kinematics or kinetics during weight-bearing tasks (e.g., stair negotiation, walking, running, landings) between individuals with knee disorders and controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), and evidence gap maps were created.

RESULTS

A total of 81 studies investigating trunk biomechanics across six different knee disorders were included (i.e., knee osteoarthritis [OA], total knee arthroplasty [TKA], patellofemoral pain [PFP], patellar tendinopathy [PT], anterior cruciate ligament deficiency [ACLD], and anterior cruciate ligament reconstruction [ACLR]). Individuals with knee OA presented greater trunk flexion during squatting (SMD 0.88, 95% CI 0.58-1.18) and stepping tasks (SMD 0.56, 95% CI 0.13-.99); ipsilateral and contralateral trunk lean during walking (SMD 1.36; 95% CI 0.60-2.11) and sit-to-stand (SMD 1.49; 95% CI 0.90-2.08), respectively. Greater trunk flexion during landing tasks in individuals with PFP (SMD 0.56; 95% CI 0.01-1.12) or ACLR (SMD 0.48; 95% CI 0.21-.75) and greater ipsilateral trunk lean during single-leg squat in individuals with PFP (SMD 1.01; 95% CI 0.33-1.70) were also identified. No alterations in trunk kinematics of individuals with TKA were identified. Evidence gap maps outlined the lack of investigations for individuals with PT or ACLD, as well as for trunk kinetics across knee disorders.

CONCLUSION

Individuals with knee OA, PFP, or ACLR present with altered trunk kinematics in the sagittal and frontal planes. The findings of this review support the assessment of trunk biomechanics in these individuals in order to identify possible targets for rehabilitation and avoidance strategies.

TRIAL REGISTRATION

PROSPERO registration number: CRD42019129257.

What is the Effect of Changing Running Step Rate on Injury, Performance and Biomechanics? A Systematic Review and Meta-analysis

Background

Running-related injuries are prevalent among distance runners. Changing step rate is a commonly used running retraining strategy in the management and prevention of running-related injuries.

Objective

The aims of this review were to synthesise the evidence relating to the effects of changing running step rate on injury, performance and biomechanics.

Design

Systematic review and meta-analysis.

Data Sources

MEDLINE, EMBASE, CINAHL, and SPORTDiscus.

Results

Thirty-seven studies were included that related to injury (n = 2), performance (n = 5), and biomechanics (n = 36). Regarding injury, very limited evidence indicated that increasing running step rate is associated with improvements in pain (4 weeks: standard mean difference (SMD), 95% CI 2.68, 1.52 to 3.83; 12 weeks: 3.62, 2.24 to 4.99) and function (4 weeks: 2.31, 3.39 to 1.24); 12 weeks: 3.42, 4.75 to 2.09) in recreational runners with patellofemoral pain. Regarding performance, very limited evidence indicated that increasing step rate increases perceived exertion ( − 0.49,  − 0.91 to − 0.07) and awkwardness (− 0.72, − 1.38 to − 0.06) and effort (− 0.69, − 1.34, − 0.03); and very limited evidence that an increase in preferred step rate is associated with increased metabolic energy consumption (− 0.84, − 1.57 to − 0.11). Regarding biomechanics, increasing running step rate was associated with strong evidence of reduced peak knee flexion angle (0.66, 0.40 to 0.92); moderate evidence of reduced step length (0.93, 0.49 to 1.37), peak hip adduction (0.40, 0.11 to 0.69), and peak knee extensor moment (0.50, 0.18 to 0.81); moderate evidence of reduced foot strike angle (0.62, 034 to 0.90); limited evidence of reduced braking impulse (0.64, 0.29 to 1.00), peak hip flexion (0.42, 0.10 to 0.75), and peak patellofemoral joint stress (0.56, 0.07 to 1.05); and limited evidence of reduced negative hip (0.55, 0.20 to 0.91) and knee work (0.84, 0.48 to 1.20). Decreasing running step rate was associated with moderate evidence of increased step length (− 0.76, − 1.31 to − 0.21); limited evidence of increased contact time (− 0.95, − 1.49 to − 0.40), braking impulse (− 0.73, − 1.08 to − 0.37), and negative knee work (− 0.88, − 1.25 to − 0.52); and limited evidence of reduced negative ankle work (0.38, 0.03 to 0.73) and negative hip work (0.49, 0.07 to 0.91).

Conclusion

In general, increasing running step rate results in a reduction (or no change), and reducing step rate results in an increase (or no change), to kinetic, kinematic, and loading rate variables at the ankle, knee and hip. At present there is insufficient evidence to conclusively determine the effects of altering running step rate on injury and performance. As most studies included in this review investigated the immediate effects of changing running step rate, the longer-term effects remain largely unknown.

Prospero Registration

CRD42020167657.

Leaning the Trunk Forward Decreases Patellofemoral Joint Loading During Uneven Running

ABSTRACT

AminiAghdam, S, Epro, G, James, D, and Karamanidis, K. Leaning the trunk forward decreases patellofemoral joint loading during uneven running. J Strength Cond Res 36(12): 3345-3351, 2022-Although decline surfaces or a more upright trunk posture during running increase the patellofemoral joint (PFJ) contact force and stress, less is known about these kinetic parameters under simultaneous changes to the running posture and surface height. This study aimed to investigate the interaction between Step (10-cm drop-step and level step) and Posture (trunk angle from the vertical: self-selected, ∼15°; backward, ∼0°; forward, ∼25°) on PFJ kinetics (primary outcomes) and knee kinematics and kinetics as well as hip and ankle kinetics (secondary outcomes) in 12 runners at 3.5 ms -1 . Two-way repeated measures analyses of variance ( α = 0.05) revealed no step-related changes in peak PFJ kinetics across running postures; however, a decreased peak knee flexion angle and increased joint stiffness in the drop-step only during backward trunk-leaning. The Step main effect revealed significantly increased peak hip and ankle extension moments in the drop-step, signifying pronounced mechanical demands on these joints. The Posture main effect revealed significantly higher and lower PFJ kinetics during backward and forward trunk-leaning, respectively, when compared with the self-selected condition. Forward trunk-leaning yielded significantly lower peak knee extension moments and higher hip extension moments, whereas the opposite effects occurred with backward trunk-leaning. Overall, changes to the running posture, but not to the running surface height, influenced the PFJ kinetics. In line with the previously reported efficacy of forward trunk-leaning in mitigating PFJ stress while even or decline running, this technique, through a distal-to-proximal joint load redistribution, also seems effective during running on surfaces with height perturbations.

The Effectiveness of Gait Retraining on Running Kinematics, Kinetics, Performance, Pain, and Injury in Distance Runners: A Systematic Review With Meta-analysis

OBJECTIVE

To evaluate the effectiveness of running gait retraining on kinematics, kinetics, performance, pain, and injury in distance runners.

DESIGN

Intervention systematic review with meta-analysis.

LITERATURE SEARCH

Seven electronic databases from inception to March 2021.

TRIAL SELECTION CRITERIA

Randomized controlled trials that (1) evaluated running gait retraining compared to no intervention, usual training, placebo, or standard care and (2) reported biomechanical, physiological, performance, or clinical outcomes.

DATA SYNTHESIS

Random-effects metaanalyses were completed, and the certainty of evidence was judged using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. We categorized interventions into step rate, non-rearfoot footstrike, impact, ground contact time, and multiparameter subgroups.

RESULTS

We included 19 trials (673 participants). Moderate-certainty evidence indicated step rate gait retraining increased step rate (SMD 1.03 [95% confidence interval {CI}: 0.63, 1.44]; number of trials (N): 4; I²: 0%) and reduced average vertical loading rate (SMD -0.57 [95% CI, -1.05 to -0.09], N: 3; I²: 0%). Low-certainty evidence indicated non-rearfoot footstrike retraining increased knee flexion at initial contact (SMD 0.74 [95% CI, 0.11 to 1.37]; N: 2; I²: 0%), but did not alter running economy (SMD 0.21 [95% CI, -1.11 to 1.52]; N: 3; I²: 19%).). Low-certainty evidence indicated multiparameter retraining did not alter running economy (SMD 0.32 [-0.39, 1.02]; N: 3; I²: 19%) or performance (SMD 0.14 [95% CI, -4.87 to 4.58]; N: 2; I²: 18%). Insufficient trials reported on pain outcomes. Two trials demonstrated reduced 1-year injury incidence following gait retraining.

CONCLUSIONS

Gait retraining interventions altered step rate and knee kinematics, lowered vertical loading rates, and did not affect running performance. J Orthop Sports Phys Ther 2022;52(4):192-206. Epub 05 Feb 2022. doi:10.2519/jospt.2022.10585.

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.

Hip muscle activity in male football players with hip-related pain; a comparison with asymptomatic controls during walking

OBJECTIVES

Compare muscle activity between male football players with and without hip-related pain. Morphological and intra-articular features of hip-related pain are proposed pre-cursors to hip osteoarthritis. Altered muscle activity is a feature of severe hip osteoarthritis, but it is not known whether differences exist earlier in the pathological spectrum.

DESIGN

Cross-sectional; SETTING: University laboratory; PARTICIPANTS: Forty-two male football players with hip-related pain; and 19 asymptomatic controls.

MAIN OUTCOME MEASURES

Hip muscle activity (Gluteus maximus, gluteus medius, tensor facia latae, adductor longus and rectus femoris) was recorded during walking using surface electromyography (EMG).

RESULTS

Men with hip-related pain had sustained rectus femoris activity prior to toe-off (47-51% of the gait cycle) (p = 0.01, ES = 0.51) unlike controls who had reduced activity. In men with severe hip-related pain, gluteus maximus EMG was sustained into mid-stance (12-20% of the gait cycle) (F = 6.15, p < 0.01) compared to controls.

CONCLUSIONS

Differences in rectus femoris and gluteus maximus activity were identified between male footballers with and without hip-related pain. The pattern of gluteus maximus EMG relative to peak, approaching mid-stance in severe hip-related pain, is consistent with observations in severe hip osteoarthritis. This supports the hypothesis that symptom severity may influence muscle activity across the spectrum of hip degeneration.

The immediate effect of foot orthoses on gluteal and lower limb muscle activity during overground walking in healthy young adults

BACKGROUND

Although foot orthoses are often used in the management of lower limb musculoskeletal conditions, their effects on muscle activation is unclear, especially in more proximal segments of the lower limb.

RESEARCH QUESTION

Primary aim: Is there an immediate effect of foot orthoses on gluteal muscle activity during overground walking in healthy young adults? Secondary aim: Is there an immediate effect of foot orthoses on the activity of hamstring, quadriceps and calf muscles?

METHODS

In eighteen healthy young adults, muscle activity was recorded using fine wire electrodes for gluteus minimus (GMin; anterior, posterior) and gluteus medius (GMed; anterior, middle, posterior); and surface electrodes for gluteus maximus (GMax), hamstring, quadriceps and calf muscles. Participants completed six walking trials for two conditions; shoe and shoe with prefabricated foot orthoses. Muscle activity was normalised to the peak activity of the shoe condition and analysed using one-dimensional statistical non-parametric mapping to identify differences across the gait cycle.

RESULTS

Activity of GMed (anterior, middle, posterior) and GMin (posterior) was reduced in early stance phase when the orthosis was worn in the shoe (p < 0.05). GMin (anterior) activity was significantly reduced during swing (p < 0.05). Muscle activity was also significantly reduced during the orthoses condition for the lateral hamstrings and calf muscles (p < 0.05).

SIGNIFICANCE

Using foot orthoses may provide a strategy to reduce demand on GMin, GMed, lateral hamstring and calf muscles while walking.

Running Biomechanics Before Injury and 1 Year After Anterior Cruciate Ligament Reconstruction in Division I Collegiate Athletes

BACKGROUND

Preinjury running biomechanics are an ideal comparator for quantifying recovery after anterior cruciate ligament (ACL) reconstruction (ACLR), allowing for assessments within the surgical and nonsurgical limbs. However, availability of preinjury running biomechanics is rare and has been reported in case studies only.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine if running biomechanics return to preinjury levels within the first year after ACLR among collegiate athletes. We hypothesized that (1) surgical knee biomechanics would be significantly reduced shortly after ACLR and would not return to preinjury levels by 12 months and (2) nonsurgical limb mechanics would change significantly from preinjury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Thirteen Division I collegiate athletes were identified between 2015 and 2020 (6 female; mean ± SD age, 20.7 ± 1.3 years old) who had whole body kinematics and ground-reaction forces recorded during treadmill running (3.7 ± 0.6 m/s) before sustaining an ACL injury. Running analyses were repeated at 4, 6, 8, and 12 months (4M, 6M, 8M, 12M) after ACLR. Linear mixed effects models were used to assess differences in running biomechanics between post-ACLR time points and preinjury within each limb, reported as Tukey-adjusted P values.

RESULTS

When compared with preinjury, the surgical limb displayed significant deficits at all postoperative assessments (P values <.01; values reported as least squares mean difference [SE]): peak knee flexion angle (4M, 13.2° [1.4°]; 6M, 9.9° [1.4°]; 8M, 9.8° [1.4°]; 12M, 9.0° [1.5°]), peak knee extensor moment (N·m/kg; 4M, 1.32 [0.13]; 6M, 1.04 [0.13]; 8M, 1.04 [0.13]; 12M, 0.87 [0.15]; 38%-57% deficit), and rate of knee extensor moment (N·m/kg/s; 4M, 22.7 [2.4]; 6M, 17.9 [2.3]; 8M, 17.5 [2.4]; 12M, 16.1 [2.6]; 33%-46% deficit). No changes for these variables from preinjury (P values >.88) were identified in the nonsurgical limb.

CONCLUSION

After ACLR, surgical limb knee running biomechanics were not restored to the preinjury state by 12M, while nonsurgical limb mechanics remained unchanged as compared with preinjury. Collegiate athletes after ACLR demonstrate substantial deficits in running mechanics as compared with preinjury that persist beyond the typical return-to-sport time frame. The nonsurgical knee appears to be a valid reference for recovery of the surgical knee mechanics during running, owing to the lack of change within the nonsurgical limb.

Patients with chronic unilateral anterior knee pain experience bilateral deficits in quadriceps function and lower quarter flexibility: a cross-sectional study

Background: Little is known about how chronic unilateral anterior knee pain (AKP) affects bilateral quadriceps function and lower quarter flexibility. Objective: To determine if patients with chronic unilateral AKP present bilateral deficits in quadriceps function and lower quarter flexibility. Methods: Twenty-two patients with chronic unilateral AKP (pain duration: 48.6 months) and 22 matched healthy controls were evaluated. Pain perception and functional outcomes were obtained. Knee joint and thigh circumferences, quadriceps subcutaneous tissue thickness and function (i.e. maximal and explosive strength, activation, and endurance), and lower quarter flexibility (i.e. hamstrings and iliopsoas/rectus femoris muscle) in both legs were compared across conditions. Results: Knee joint and thigh circumferences, and quadriceps subcutaneous tissue thickness were not different between conditions (P ≥ .39). Compared with matched healthy controls, patients with chronic unilateral AKP showed: 1) greater pain perception (0.0 versus 4.4 cm, P < .0001); 2) a lower score for functional outcomes (79.6 versus 53.9, P < .0001); 3) less bilateral quadriceps maximal (3.5 versus 2.8 Nm/kg, P < .0001) and explosive (10.8 versus 8.7 Nm/kg/s, P = .01) strength, activation (0.95 versus 0.83, P < .0001), and endurance (1.66 versus 1.52 Nm/kg, P = .02); and 4) less bilateral hamstrings (86.8 versus 72.6°, P = .002) and iliopsoas/rectus femoris (11.6 versus 7.8°, P < .05) flexibility. Conclusion: Patients with chronic unilateral AKP (without knee joint effusion or quadriceps muscle atrophy) appear to have bilateral deficits in quadriceps function and lower quarter flexibility, which should be addressed with pain reduction.

Changes In Gait Biomechanics As Functional Symptom Of Chondromalacia Patella

The goal of this research was to investigate functional and biomechanical symptoms in patients with chondromalacia patella. Material and Methods — Gait biomechanics was assessed in 35 patients with diagnosed unilateral chondromalacia patella and in 20 healthy adult controls. We recorded hip and knee movements, impact loads and temporal characteristics of the gait cycle (GC) during self-paced walking. Results — The temporal characteristics of gait and the impact loads remained normal in the patient population. Hip flexion amplitude decreased both on the affected (p=0.002) vs. unaffected (p=0.016) sides, compared to healthy control, whereas the amplitude phase increased on the affected (p=0.012) vs. unaffected (p=0.001) sides, versus healthy control. Hip extension and adduction-abduction amplitudes did not change significantly. Stance-phase and swing-phase knee flexion amplitudes did not change significantly. Knee extension amplitude on the affected limb increased (p=0.015), and knee rotation on the unaffected limb decreased versus control (p=0.016). The so-called stairstep symptom defined in the study was found in 83% of patients: in 23 patients bilaterally and in 6 patients unilaterally. Conclusion — Chondromalacia patella affected the gait biomechanics on both sides. The changes in the kinematic patterns during the flat-surface walking were not substantial. The only pathognomonic functional symptom of the condition was the stairstep symptom.

Uneven running: How does trunk-leaning affect the lower-limb joint mechanics and energetics?

This study aimed to investigate the role of trunk posture in running locomotion. Twelve recreational runners ran in the laboratory across even and uneven ground surface (expected 10 cm drop-step) with three trunk-lean angles from the vertical (self-selected, ∼15°; anterior, ∼25°; posterior, ∼0°) while 3D kinematic and kinetic data were collected using a 3D motion-capture-system and two embedded force-plates. Two-way repeated measures ANOVAs (α = 0.05) compared lower-limb joint mechanics (angles, moments, energy absorption and generation) and ground-reaction-force parameters (braking and propulsive impulse) between Step (level and drop) and Posture conditions. The Step-by-Posture interaction revealed decreased hip energy generation, and greater peak knee extension moment in the drop-step during running with posterior versus anterior trunk-lean. Furthermore, energy absorption across hip and ankle nearly doubled in the drop-step across all running conditions. The Step main effect revealed that the knee and ankle energy absorption, ankle energy generation, ground-reaction-force, and braking impulse significantly increased in the drop-step. The Posture main effect revealed that, compared with a self-selected trunk-lean, the knee's energy absorption/generation, ankle's energy generation and the braking impulse were either retained or attenuated when leaning the trunk anteriorly. The opposite effects occurred with a posterior trunk-lean. In conclusion, while the pronounced mechanical ankle stress in drop-steps is marginally affected by posture, changing the trunk-lean reorganizes the load distribution across the knee and hip joints. Leaning the trunk anteriorly in running shifts loading from the knee to the hip not only in level running but also when coping with ground-level changes.Highlights Changing the trunk-lean when running reorganizes the load distribution across the knee and hip joints.Leaning the trunk anteriorly from a habitual trunk posture during running attenuates the mechanical stress on the knee, while the opposite effect occurs with a posterior trunk-lean, irrespective to the ground surface uniformity.The effect of posture on pronounced mechanical ankle stress in small perturbation height during running is marginal.Leaning the trunk anteriorly shifts loading from the knee to the hip not only in level running but also when coping with small perturbation height.

Gait retraining for runners with patellofemoral pain: A protocol for systematic review and meta-analysis

INTRODUCTION

Patellofemoral pain (PFP) is highly prevalent in runners. Physical therapies were proved to be effective in the treatment of PFP. Gait retraining is an important method of physical therapy, but its effectiveness and safety for PFP remained controversial. Previous review suggests gait retraining in the treatment of PFP warrants consideration. However, recent publications of randomized controlled studies and case series studies indicated the positive effect of gait retraining in clinical and functional outcomes, which re-raise the focus of gait retraining. This paper will systematically review the available evidence, assessing the safety and effectiveness for the use of gait retraining for runners with PEP.

METHOD AND ANALYSIS

A systematic review of relevant studies in Pubmed, Embase, SCOPUS, and Cochrane Library were synthesized. Inclusion criteria are studies evaluating clinical outcomes (i.e., changes to pain and/or function) following running retraining interventions in symptomatic running populations; Studies with less than 10 participants in total or in the running retraining intervention group were excluded. The primary outcomes measured will be pain score, Lower extremity functional scale and training related injuries or complications. Review Manager (Revman Version 5.3) software will be used for data synthesis, sensitivity analysis, meta regression, subgroup analysis and risk of bias assessment. A funnel plot will be developed to evaluate reporting bias and Begg and Egger tests will be used to assess funnel plot symmetries. We will use the Grading of Recommendations Assessment, Development and Evaluation system to assess the quality of evidence.

ETHICS AND DISSEMINATION

Our aim is to publish this systematic review in a peer-reviewed journal. Our findings will provide information about the safety of gait retraining and their effect on reliving pain and improving function of lower limb on runners with PEP. This review will not require ethical approval as there are no issues about participant privacy.

Effects of gait retraining with focus on impact versus gait retraining with focus on cadence on pain, function and lower limb kinematics in runners with patellofemoral pain: Protocol of a randomized, blinded, parallel group trial with 6-month follow-up

Patellofemoral pain (PFP) is one of the most prevalent injuries in runners. Unfortunately, a substantial part of injured athletes do not recover fully from PFP in the long-term. Although previous studies have shown positive effects of gait retraining in this condition, retraining protocols often lack clinical applicability because they are time-consuming, costly for patients and require a treadmill. The primary objective of this study will be to compare the effects of two different two-week partially supervised gait retraining programs, with a control intervention; on pain, function and lower limb kinematics of runners with PFP. It will be a single-blind randomized clinical trial with six-month follow-up. The study will be composed of three groups: a group focusing on impact (group A), a group focusing on cadence (group B), and a control group that will not perform any intervention (group C). The primary outcome measure will be pain assessed using the Visual Analog Pain scale during running. Secondary outcomes will include pain during daily activities (usual), symptoms assessed using the Patellofemoral Disorders Scale and lower limb running kinematics in the frontal (contralateral pelvic drop; hip adduction) and sagittal planes (foot inclination; tibia inclination; ankle dorsiflexion; knee flexion) assessed using the MyoResearch 3.14-MyoVideo (Noraxon U.S.A. Inc.). The study outcomes will be evaluated before (t0), immediately after (t2), and six months (t24) after starting the protocol. Our hypothesis is that both partially supervised gait retraining programs will be more effective in reducing pain, improving symptoms, and modifying lower limb kinematics during running compared with the control group, and that the positive effects from these programs will persist for six months. Also, we believe that one gait retraining group will not be superior to the other. Results from this study will help improve care in runners with PFP, while maximizing clinical applicability as well as time and cost-effectiveness.

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.

The Risk of Knee Osteoarthritis in Professional Soccer Players—a Systematic Review With Meta-Analyses

BACKGROUND

We address the question whether professional soccer players with and without macroinjury of the knee joint are at an elevated risk for knee osteoarthritis.

METHODS

A systematic review with meta-analyses was conducted. The study protocol was prospectively registered (registration number CRD42019137139). The MEDLINE, EMBASE, and Web of Science databases were searched for relevant publications; in addition, forward searching was performed, and the listed references were considered. All steps of the process were undertaken independently by two reviewers, and any discordances were resolved by consensus. For all publications whose full text was included, the methods used were critically evaluated. The quality of the evidence was judged using the GRADE criteria.

RESULTS

The pooled odds ratio for objectively ascertained osteoarthrosis of the knee was 2.25 (95% confidence interval [1.41-3.61], I2 = 71%). When only radiologically ascertained knee osteoarthrosis was considered, the odds ratio was 3.98 [1.34; 11.83], I2 = 58%). The pooled risk estimator in studies in which knee joint macroinjury was excluded was 2.81 ([1.25; 6.32], I2 = 71%).

CONCLUSION

A marked association was found between soccer playing and knee osteoarthritis in male professional soccer players. For female professional soccer players, the risk of knee osteoarthritis could not be assessed because of the lack of data. Knee injuries seem to play an important role in the development of knee osteoarthritis in professional soccer players.

A Contemporary Approach to Patellofemoral Pain in Runners

Patellofemoral pain (PFP) is among the most common injuries in recreational runners. Current evidence does not identify alignment, muscle weakness, and patellar maltracking or a combination of these as causes of PFP. Rather than solely investigating biomechanics, we suggest a holistic approach to address the causes of PFP. Both external loads, such as changes in training parameters and biomechanics, and internal loads, such as sleep and psychological stress, should be considered. As for the management of runners with PFP, recent research suggested that various interventions can be considered to help symptoms, even if these interventions target biomechanical factors that may not have caused the injury in the first place. In this Current Concepts article, we describe how the latest evidence on education about training modifications, strengthening exercises, gait and footwear modifications, and psychosocial factors can be applied when treating runners with PFP. The importance of maintaining relative homeostasis between load and capacity will be emphasized. Recommendations for temporary or longer-term interventions will be discussed. A holistic, evidence-based approach should consist of a graded exposure to load, including movement, exercise, and running, while considering the capacity of the individual, including sleep and psychosocial factors. Cost, accessibility, and the personal preferences of patients should also be considered.

Pericapsular hip muscle activity in people with and without femoroacetabular impingement. A comparison in dynamic tasks

OBJECTIVES

Compare anterior pericapsular muscle activity between individuals with and without femoroacetabular impingement syndrome (FAIS) during dynamic tasks, to investigate whether muscle activity is consistent with a role in retracting the capsule to prevent impingement and active restraint of the femoral head in walking.

DESIGN

Cross-sectional.

SETTING

University-laboratory.

PARTICIPANTS

Thirteen athletes with FAIS and 13 pain-free controls.

MAIN OUTCOME MEASURES

Muscle activity was recorded using fine-wire (Iliocapsularis, iliacus and anterior gluteus minimus) and surface (rectus femoris) electromyography (EMG), during three hip flexion tasks (active and assisted hip flexion; squatting) and four walking trials.

RESULTS

Iliocapsularis EMG amplitude was no different between active and assisted hip flexion tasks around 90° of hip flexion in FAIS. There was no difference in EMG between groups in squatting. The pattern of burst activity preceding peak hip extension in iliacus, iliocapsularis, and anterior gluteus minimus was similar in both groups during walking.

CONCLUSION

In FAIS, similar activation of iliocapsularis during active and assisted hip flexion, despite reduced flexion torque demand in the latter, suggests a role in capsular retraction or enhanced hip joint protection. Pericapsular muscle activity in advance of peak hip extension during walking is consistent with a proposed contribution to femoral head control.

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.

Use of Wearables: Tracking and Retraining in Endurance Runners

Wearable devices are ubiquitous among runners, coaches, and clinicians with an ever-increasing number of devices coming on the market. In place of gold standard measures in the laboratory, these devices attempt to provide a surrogate means to track running biomechanics outdoors. This review provides an update on recent literature in the field of wearable devices in runners, with an emphasis on criterion validity and usefulness in the coaching and rehabilitation of runners. Our review suggests that while enthusiasm should be tempered, there is still much for runners to gain with wearables. Overall, our review finds evidence supporting the use of wearables to improve running performance, track global training loads applied to the runner, and provide real-time feedback on running speed and run cadence. Case studies illustrate the use of wearables for the purposes of performance and rehabilitation.

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.

Association Between Temporal Spatial Parameters and Overuse Injury History in Runners: A Systematic Review and Meta-analysis

BACKGROUND

Temporal spatial parameters during running are measurable outside of clinical and laboratory environments using wearable technology. Data from wearable technology may be useful for injury prevention, however the association of temporal spatial parameters with overuse injury in runners remains unclear.

OBJECTIVE

To identify the association between overuse injury and temporal spatial parameters during running.

DATA SOURCES

Electronic databases were searched using keywords related to temporal spatial parameters, running, and overuse injury, and authors' personal article collections through hand search.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Articles included in this systematic review contained original data, and analytically compared at least one temporal spatial parameter (e.g. cadence) between uninjured and retrospectively or prospectively injured groups of runners. Articles were excluded from this review if they did not meet these criteria or measured temporal spatial parameters via survey.

STUDY APPRAISAL AND SYNTHESIS METHOD

The internal validity of each article was assessed using the National Institutes of Health Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Meta-analyses were conducted for temporal spatial parameters if data existed from at least three separate cohorts of the same prospective or retrospective design. Data were pooled and analyzed using an inverse variance fixed-effect model.

RESULTS

Thirteen articles which tested a total of 24 temporal spatial parameters during running were included in the review. Meta-analyses were conducted on four temporal spatial parameters using data from eleven retrospective studies. Healthy runners and those with a history of overuse injury had a similar average stride time (mean difference: 0.00 s, 95% CI - 0.01 to 0.01 s), contact time (mean difference: 0.00 s, 95% CI 0.00 to 0.01 s), cadence (mean difference: 0.3 steps per minute (spm), 95% CI - 1.8 to 2.5 spm), and stride length (mean difference 0.00 m, 95% CI - 0.05 to 0.05 m) during running.

LIMITATIONS

Data pooled for meta-analyses were limited to retrospective design studies. Studies included in the systematic review had low methodological consistency.

CONCLUSION

Based on pooled results from multiple studies, stride time, contact time, cadence, and stride length averages are not distinguishable between runners either with or without a history of overuse injury. More prospective studies are required to determine the association of temporal spatial parameters with overuse injury development in runners.

SYSTEMATIC REVIEW REGISTRATION REGISTRY AND NUMBER

CRD42018112290.

The effect of altered stride length on iliocapsularis and pericapsular muscles of the anterior hip: An electromyography investigation during asymptomatic gait

BACKGROUND

Anterior pericapsular muscles potentially contribute to active hip joint stability in walking by controlling anterior femoral translation in peak extension. Alternatively, these muscles could flex the hip and tension the anterior capsule to aid initiation of swing. Although never investigated, the location of Iliocapsularis and its extensive anterior hip capsule attachment imply a potential role in these functions. We hypothesised if these muscles contribute to control of femoral head translation (rather than hip flexion), their activation would decrease when peak hip extension is reduced during shorter stride walking.

RESEARCH QUESTIONS

To provide the first description of iliocapsularis activity during walking and challenge the hypothesised roles of the anterior pericapsular hip muscles in gait by walking with shortened strides.

METHODS

Fifteen healthy volunteers walked with self-selected and shortened stride lengths. Electromyographic recordings were made from iliocapsularis, iliacus and anterior gluteus minimus with intramuscular electrodes, and rectus femoris with surface electrodes. Stride characteristics were measured using force sensors and 3D motion capture. Ensembles of burst activity profiles for each stride length were compared.

RESULTS

Iliocapsularis displayed a consistent EMG burst around toe-off (terminal hip extension) that peaked during early swing phase with self-selected strides. In shortened strides, iliocapsularis EMG increased during mid to late stance (p = 0.03), with no difference in other muscles. Iliocapsularis, iliacus and rectus femoris activity decreased during early stance (p < 0.01) in short strides, whereas gluteus minimus EMG increased (p = 0.03).

SIGNIFICANCE

Iliocapsularis displayed an EMG burst around toe-off during walking, and greater EMG during mid-late stance in short stride walking, which was not seen in other pericapsular muscles. Shortened strides increase the demand for active tensioning of the hip joint capsule in initial swing, and suggests a role for iliocapsularis during active hip flexion in pain free young individuals.

Skipping has lower knee joint contact forces and higher metabolic cost compared to running

BACKGROUND

The health benefits of running based exercise programs are plentiful however the high rate of injury in these programs often reduces or eliminates exercise participation. Skipping has shorter steps, reduced vertical ground reaction forces (GRFs), and lower knee extensor torques, compared to running forming the basis of the present hypothesis that skipping would have lower tibio-femoral and patello-femoral joint contact forces.

RESEARCH QUESTION

The purpose of this study was to compare knee contact forces between skipping and running at the same speed. We also compared metabolic cost of these two gaits to examine the idea that the larger vertical displacement in skipping is a primary factor in its previously reported high metabolic cost.

METHODS

The study evaluated joint contact forces through musculoskeletal modeling with GRF and 3D kinematic data and metabolic cost using oxygen consumption data from 20 young, healthy, trained participants as they skipped and ran on an instrumented treadmill at 2.68 m/s.

RESULTS

Skipping, compared to running, had substantially lower tibio-femoral and patello-femoral joint contact forces and linear impulses on both per-step and per-kilometer (i.e. lower cumulative loads) bases and also 30% higher metabolic cost. The lower joint loads in skipping were directly associated with its shorter steps and the higher metabolic cost was directly associated to its larger vertical displacement through the stride.

SIGNIFICANCE

As joint loads may predispose individuals to running related injuries, skipping presents an attractive alternative exercise modality with additional increased aerobic benefits.

Patellofemoral joint stress measured across three different running techniques

BACKGROUND

Patellofemoral pain (PFP) is the most common running-related injury. It has been shown in previous studies that gait retraining may have a beneficial effect on patellofemoral joint stress (PFJS).

RESEARCH QUESTION

Is there a reduction of PFJS across 4 running conditions: 1. runner's typical rearfoot strike pattern, 2. forefoot landing, 3. step rate increase by 10% and 4. forward trunk lean?

METHODS

Nineteen healthy runners (28.05 ± 5.03 years; 26.58 ± 8.85 km/week, 6.00 ± 4.51 years of running experience) completed one running trial for each condition, at the same subject-specific comfortable speed on a treadmill. Kinetic and kinematic data were collected and measures of hip, knee and ankle joint moments and PFJS were calculated.

RESULTS

Compared to rearfoot strike condition, peak PFJS and PFJS-time integral per step were significantly (P < 0.01) lower during forefoot landing and step rate increase conditions. PFJS per kilometer was significantly reduced for forefoot landing (17.01%; P < 0.01) and increased step rate (12.90%; P = 0.003). Forward trunk lean technique showed no significant differences in peak PFJS (P = 0.187), PFJS-time integral per step (P = 0.815) and PFJS per kilometer (P = 0.077) compared to rearfoot strike pattern.

INTERPRETATION

The comparison between techniques revealed greater reductions on PFJS by forefoot landing, followed by 10% step rate increase condition. These changes were the result of different lower limb movement strategies across the 2 running conditions. We conclude that compared to a rearfoot strike pattern, both a forefoot landing and step rate increase result in lower cumulative PFJS joint stress in healthy runners, with the forefoot landing being the most effective. These running technique modifications could be recommended to reduce PFJS loads and may have implications for PFP prevention.

The effects & mechanisms of increasing running step rate: A feasibility study in a mixed-sex group of runners with patellofemoral pain

OBJECTIVES

To explore feasibility of recruitment and retention of runners with patellofemoral pain (PFP), before delivering a step rate intervention.

DESIGN

Feasibility study.

SETTING

Human performance laboratory.

PARTICIPANTS

A mixed-sex sample of runners with PFP (n = 11).

MAIN OUTCOME MEASURES

Average/worst pain and the Kujala Scale were recorded pre/post intervention, alongside lower limb kinematics and surface electromyography (sEMG), sampled during a 3 KM treadmill run.

RESULTS

Recruitment and retention of a mixed-sex cohort was successful, losing one participant to public healthcare and with kinematic and sEMG data lost from single participants only. Clinically meaningful reductions in average (MD = 2.1, d = 1.7) and worst pain (MD = 3.9, d = 2.0) were observed. Reductions in both peak knee flexion (MD = 3.7°, d = 0.78) and peak hip internal rotation (MD = 5.1°, d = 0.96) were observed, which may provide some mechanistic explanation for the identified effects. An increase in both mean amplitude (d = 0.53) and integral (d = 0.58) were observed for the Vastus Medialis Obliqus (VMO) muscle only, of questionable clinical relevance.

CONCLUSIONS

Recruitment and retention of a mixed sex PFP cohort to a step rate intervention involving detailed biomechanical measures is feasible. There are indications of both likely efficacy and associated mechanisms. Future studies comparing the efficacy of different running retraining approaches are warranted.

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.

Sex-specific kinetic and kinematic indicators of medial tibiofemoral force during walking and running

BACKGROUND

Our aims were to (1) Evaluate sex-specific contributions of peak knee flexion moment (pKFM) and peak knee adduction moment (pKAM) in medial tibiofemoral joint (TFJ) force during walking and running; (2) identify kinematic variables to estimate peak medial TFJ force.

METHODS

Eighty-seven runners participated (36 females, 51 males; age=23.0±3.8years (1 standard deviation)). Kinematics and kinetics data were collected during treadmill walking (1.3m/s) and running (3.0±0.4m/s). Peak medial TFJ contact force was estimated using a musculoskeletal model. Linear regression analyses were used to assess the contribution of pKFM, pKAM and kinematic indicators to estimated joint forces.

RESULTS

During walking and running, pKAM and pKFM accounted for 74.9% and 64.5% of peak medial TFJ force variance (P<0.001), respectively. Similar pKAM contribution was found between males and females during walking (51.8% vs. 47.9%), as opposed to running (50.4% vs. 26.8%). Kinematic indicators during walking were peak knee flexion and adduction angles, regardless of sex. During running, indicators were ankle dorsiflexion at foot strike and center of mass (COM) vertical displacement in females (R²=0.364, P=0.012), and peak knee abduction angle and step length in males (R²=0.508, P=0.019).

CONCLUSION

We conclude from these results that pKAM and pKFM make significant but potentially sex-specific contributions to peak medial TFJ force during walking and running. Clinically, peak medial TFJ force during walking can be estimated using peak knee flexion and adduction angles in both sexes. During running, ankle dorsiflexion at foot strike and COM oscillation are best indicators among females, while knee abduction and step length are best among males.

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.

Lower extremity joint loads in habitual rearfoot and mid/forefoot strike runners with normal and shortened stride lengths

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2-14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: -9.9 ± 0.9, hFF-FFS: -9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one's SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads.