Patellofemoral joint kinetics during squatting in collegiate women athletes.

OBJECTIVE To characterize the biomechanics of the patellofemoral joint during squatting in collegiate women athletes. DESIGN Repeated measures experimental design. BACKGROUND Although squatting exercises are required components of most intercollegiate resistance-training programs and are commonly performed during rehabilitation, the effects of various squatting depths on patellofemoral joint stress have not been quantified. METHODS Anthropometric data, three-dimensional knee kinematics, and ground reaction forces were used to calculate the knee extensor moment (inverse dynamics approach) in five intercollegiate female athletes during squatting exercise at three different depths (approximately 70 degrees, 90 degrees and 110 degrees of knee flexion). A biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction force and patellofemoral joint stress during each trial. RESULTS Peak knee extensor moment, patellofemoral joint reaction force and patellofemoral joint stress did not vary significantly between the three squatting trials. CONCLUSIONS Squatting from 70 degrees to 110 degrees of knee flexion had little effect on patellofemoral joint kinetics. The relative constancy of the patellofemoral joint reaction force and joint stress appeared to be related to a consistent knee extensor moment produced across the three squatting depths. RELEVANCE The results of this study do not support the premise that squatting to 110 degrees places greater stress on the patellofemoral joint than squatting to 70 degrees. These findings may have implications with respect to the safe design of athletic training regimens and rehabilitation programs.