Females with knee osteoarthritis use a detrimental knee loading strategy when squatting.

BACKGROUND: The purpose of this study was to identify sex differences in lower limb kinematics, kinetics, and muscle activation patterns between individuals with osteoarthritis and healthy controls during a two-legged squat. METHOD: Thirty OA (15 females) and 30 healthy (15 females) participants performed three 2-legged squats. Sagittal and frontal plane hip, knee, and ankle kinematics and kinetics were calculated. Two-way ANOVAs (Sex X OA Status) were used to characterize differences in squatting strategies between sexes and between those with and without knee OA. RESULTS: A greater decrease in sagittal hip, knee, and ankle range of motion and knee joint power was observed in the OA participants compared to the healthy controls. Females with OA had significantly reduced hip and knee adduction angles compared to the healthy females and males with OA. Females also had decreased hip power, hip flexion, and hip adduction moments and knee adduction moments compared to their male counterparts, with the greatest deficits observed in the females with OA. Females with OA also had the highest magnitude of muscle activation for the quadriceps, hamstrings, and gastrocnemius throughout the squat, while males with OA showed increased activation of the vastus lateralis and medial gastrocnemius compared to the healthy males. CONCLUSIONS: OA significantly altered biomechanics and neuromuscular control during the squat, with males employing a hip-dominant strategy, allowing them to achieve a greater lower limb range of motion.

Neuromuscular adaptations in older males and females with knee osteoarthritis during weight-bearing force control.

BACKGROUND: Females exhibit significantly greater incidence, prevalence, and severity of osteoarthritis (OA) compared to males. Despite known biological, morphological, and functional differences between males and females, there has been little sex-related investigation into sex-specific biomechanical and neuromuscular responses to OA. OBJECTIVE: To identify sex-related differences in OA-affected adults and within-sex differences between healthy and OA-affected adults' muscular activation patterns during lower limb loading. METHODS: Thirty adults with OA and 36 controls completed a standing ground reaction force (GRF) matching protocol requiring participants to expose equal body weight to each leg and modulate horizontal GRFs while maintaining constant joint positions. Electromyography was plotted as a function of GRF direction to depict muscle activation patterns. Muscles were classified as a general joint stabilizer, specific joint stabilizer or moment actuator by quantifying activation patterns with a test of asymmetry, specificity index and mean direction of activity. Lower limb kinematics and kinetics were also recorded. RESULTS: In general, muscle roles as it relates to joint stability did not differ between groups. Compared to controls, both males and females with OA demonstrated greater rectus femoris activity and reduced knee rotation moments. Females with OA had significantly greater biceps femoris and gastrocnemius activity during respective lateral, and anterior-medial loading directions compared to males with OA. CONCLUSIONS: We identified fundamental differences in muscular stabilization strategies in older adults with OA as well as sex-related changes in neuromuscular function that may influence joint loading conditions and provide insight into the greater incidence of knee OA in females.