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.