Muscle strength and flexibility characteristics of people displaying excessive medial knee displacement

Objective: To determine differences in strength and range of motion (ROM) between participants who exhibit medial knee displacement (MKD) during a squat that is Corrected by a heel lift and those who do not. Design: Case control. Setting: Sports medicine research laboratory. Participants: Thirty-seven healthy subjects (control, 19; MKD, 18) with no lower-extremity injury in the past 6 months volunteered to participate. Interventions: Not applicable. Main Outcome Measures: Peak force was measured in newtons using a hand-held dynamometer and passive ROM was measured in degrees with a goniometer. Separate multi-variate analyses of variance were used to determine differences in strength and ROM between groups. Post hoc testing was used to elucidate differences between groups. Results: The MKD group had the following: greater hip external rotation strength (P=.03), increased hip extension strength (P=.01), less plantarflexion strength (P=.007), and increased hip external rotation ROM (P=.008). Conclusions: The MKD group exhibited tight and weak ankle musculature. Interventions focusing on improving strength and ROM of the ankle may improve kinematics during a squat.