Patellofemoral Joint Kinetics While Squatting with and without an External Load

Study Design Single-group repeated measures design. Objective To quantify patellofemoral joint reaction forces and stress while squatting with and without an external load. Background Although squatting exercises in the rehabilitation setting are often executed to a relatively shallow depth in order to avoid the higher joint forces associated with increased knee flexion, objective criteria for ranges of motion have not been established. Methods and Measures Fifteen healthy adults performed single-repetition squats to 90° of knee flexion without an external load and with an external load (35% of the subject's body weight [BW]). Anthropometric data, three-dimensional kinematics, and ground reaction forces were used to calculate knee extensor moments (inverse dynamics approach), while a biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction forces and patellofemoral joint stress. Data were analyzed during the eccentric (0–90°) and concentric (90–0°) phases of t...