Knee valgus is a potential risk factor for lower extremity (LE) injuries. LE movement screenings and flexibility measurements may be utilized to identify neuromuscular patterns, which contribute to knee valgus. There are few studies that have investigated how flexibility and muscular activation differ between individuals who display medial knee displacement (MKD) during a single leg squat (SLS) and those who do not. We hypothesized that flexibility and muscular activation would differ between the groups. Forty individuals completed flexibility measurements and a SLS task while EMG data were collected from eight LE muscles. Three MANOVAs were run comparing flexibility measurements, EMG data, and muscle co-activation ratios. The MKD group had significantly less dorsiflexion, greater talar glide motion, and smaller hip adductor and gluteal co-activation ratios compared to the control group. Therefore, knee valgus appears to be influenced by decreased dorsiflexion and decreased co-activation of the Hip ADD and GMed and GMax muscles
