Simulated Tibiofemoral Joint Reaction Forces for Three Previously Studied Gait Modifications in Healthy Controls.

Gait modifications, such as lateral trunk lean (LTL), medial knee thrust (MKT), and toe-in gait (TIG), are frequently investigated interventions used to slow the progression of knee osteoarthritis. The Lerner knee model was developed to estimate the tibiofemoral joint reaction forces (JRF) in the medial and lateral compartments during gait. These models may be useful for estimating the effects on the JRF in the knee as a result of gait modifications. We hypothesized that all gait modifications would decrease the JRF compared to normal gait. Twenty healthy individuals volunteered for this study (26.7 ± 4.7 years, 1.75 ± 0.1 m, 73.4 ± 12.4 kg). Ten trials were collected for normal gait as well as for the three gait modifications: LTL, MKT, and TIG. The data were used to estimate the JRF in the first and second peaks for the medial and lateral compartments of the knee via opensim using the Lerner knee model. No significant difference from baseline was found for the first peak in the medial compartment. There was a decrease in JRF in the medial compartment during the loading phase of gait for TIG (6.6%) and LTL (4.9%) and an increasing JRF for MKT (2.6%). but none was statistically significant. A significant increase from baseline was found for TIG (5.8%) in the medial second peak. We found a large variation in individual responses to gait interventions, which may help explain the lack of statistically significant results. Possible factors influencing these wide ranges of responses to gait modifications include static alignment and the impacts of variation in muscle coordination strategies used, by participants, to implement gait modifications.

Reductions in peak knee abduction moment in three previously studied gait modification strategies.

BACKGROUND: First peak internal knee abduction moment (KAM) has been associated with knee osteoarthritis. Gait modification including trunk lean, medial knee thrust, and toe-in gait have shown to reduce KAM. Due to heterogeneity between study designs, it remains unclear which strategy is most effective. We compared the effects of these modifications in healthy individuals to determine their effectiveness to reduce KAM, internal knee extension moment (KEM), and medial contact force (MCF). METHODS: Twenty healthy individuals volunteered for this study (26.7 ±â€¯4.7 years, 1.75 ±â€¯0.1 m, 73.4 ±â€¯12.4 kg). Using real-time biofeedback, we collected 10 trials for each modification using individualized gait parameters based on participants' baseline mean and standard deviation (SD). Two sizes of each modification were tested: 1-3 SD greater (toe-in and trunk lean) or lesser (knee adduction) than baseline for the first five trials and 3-5 SD greater or lesser than baseline for the last five trials. RESULTS: A significant main effect was found for KAM and KEM (p < .001). All modifications reduced KAM from baseline by at least five percent; however, only medial knee thrust and small trunk lean resulted in significant KAM reductions. Only medial knee thrust reduced KEM from baseline. MCF was unchanged. CONCLUSION: Medial knee thrust was superior to trunk lean and toe-in modifications in reducing KAM. Subsequent increases in KEM and variation in individual responses to modification suggests that future interventions should be individualized by type and magnitude to optimize KAM reductions and avoid detrimental effects.

Unintended Changes in Contralateral Limb as a Result of Acute Gait Modification.

Gait modification using real-time biofeedback is a conservative intervention associated with positive outcomes. Results from systematic reviews corroborate the effectiveness of various strategies employing real-time biofeedback for reducing estimated knee joint load. The effects on the nonmodified limb, however, remain unclear. Biomechanical changes to the nonmodified limb were investigated during unilaterally implemented medial knee thrust, lateral trunk lean, and toe-in foot progression. Nineteen healthy participants were recruited. Ten trials were completed for each gait condition including baseline. Assigned magnitude for each gait modification strategy was individualized based on the mean and SD of the gait parameter during baseline. Visual real-time biofeedback was provided. During medial knee thrust, participants' nonmodified limb presented with increased: first peak medial knee contact force, internal first peak knee extensor moment, as well as knee- and hip-flexion angles at internal first peak knee extensor moment. Observed biomechanical changes are elucidative of the body's attempt to attenuate increased external loads. These findings may carry significant implications for pathological populations. Load redistribution to the nonmodified side may result in unfavorable long-term outcomes particularly in patients with bilateral diagnosis. Future studies should explore acute and chronic changes in the nonmodified limb of individuals with knee osteoarthritis.

Changes in hip mechanics during gait modification to reduce knee abduction moment.

First peak knee abduction moment (KAM) has been associated with the severity and progression of knee osteoarthritis (KOA). Gait modifications, including lateral trunk lean (TL), medial knee thrust (MKT), and reduced foot progression (FP) have decreased KAM. However, their effects on the hip joint are poorly understood. Reduced hip abduction moment has been found to be predictive of KOA progression and has been hypothesized to represent a decreased demand on the hip musculature. Lack of studies investigating changes in hip mechanics as a result of gait modification limits our understanding of their cumulative benefit, therefore, we investigated the effects of TL, MKT, and FP on internal hip abduction moment as well as rate change in net joint reaction force. Using real-time visual biofeedback, five trials were completed for each modification. Each modification target range was individualized to 3-5 SD greater (TL and FP) or lesser (MKT) than the participants mean baseline value. Kinematics and kinetics at the hip and knee were calculated at first peak KAM. Trunk lean and MKT decreased hip abduction moment compared to baseline (p < 0.001). Trunk lean increased rate change in net joint reaction force at both the hip (p < 0.001) and knee (p < 0.001) compared to baseline. Additional research is needed to fully understand the effect of gait modifications in a clinical population, particularly the relationship between hip abduction moments and KOA progression. Although interventions such as MKT and TL can be successful in reducing KAM, their effects on hip abduction moment should be considered before clinical implementation.

The Epidemiology of Injuries in Middle School Football, 2015-2017: The Advancing Healthcare Initiatives for Underserved Students Project.

BACKGROUND: Although data exist on injuries in youth football leagues, there are limited recent data on injury incidence in middle school football. Updated injury incidence estimates can help drive the development of injury prevention strategies. PURPOSE: Describe the epidemiology of injuries in middle school football during school years 2015-2016 to 2017-2018. STUDY DESIGN: Descriptive epidemiology study. METHODS: Data originated from 9 public middle schools in Virginia during school years 2015-2016 to 2017-2018. Certified athletic trainers collected injury and athlete-exposure (AE) data from school-sanctioned games and practices in boys', football. Injury counts and rates per 1000 AEs were calculated. Injury rate ratios with 95% CIs compared rates between games and practices. RESULTS: Overall, 664 middle school boys', football injuries were reported, leading to an overall injury rate of 20.54 per 1000 AEs (95% CI, 18.98-22.11). The time loss injury rate (inclusive of injuries with participation restriction time ≥24 hours) was 9.28 per 1000 AEs (95% CI, 8.23-10.33). The injury rate was higher in competition than practice (36.19 vs 17.97 per 1000 AEs; injury rate ratio, 2.01; 95% CI, 1.69-2.40). Most injuries were to the head/face (competition, 20.6%; practice, 15.8%) and hand/wrist (competition, 18.8%; practice, 16.4%) and were diagnosed as contusions (competition, 30.9%; practice, 25.9%) and sprains (competition, 19.4%; practice, 12.6%). Competitions also had a large proportion of concussions (10.3%). Overall, 80.0% and 66.9% of injuries were due to contact in competition and practice, respectively; of these contact-related injuries, 62.1% and 41.6% were specifically player contact. CONCLUSION: Injury distributions parallel those found in previous research from middle school and other sport settings. Injury rates in middle school football were higher than those reported in previous findings in high school and college. However, caution must be taken when interpreting findings in relation to other surveillance systems with varying methodologies. Still, the findings highlight the need for injury prevention strategies within middle school football, particularly as related to contact-related mechanisms.