Patellofemoral Joint Loading During Bodyweight One-legged And Two-legged Bosu-ball And Floor Squats

PURPOSE: To quantify patellofemoral force and stress between BOSU-ball squat and floor squat, and between one-legged and two-legged squatting. METHODS: Sixteen healthy participants performed one-legged and two-legged BOSU-ball squats and floor squats. Kinematic and ground reaction force data were used to calculate resultant knee force and torque using inverse dynamics, with electromyographic data employed in a knee muscle model to predict resultant knee force and torque. A biomechanical optimization model was employed to calculate patellofemoral joint force and stress at every 10° between 10°-100° knee-angles during the squat descent and squat ascent. Repeated measures 2-way ANOVA (p < 0.01) was employed for statistical analyses. RESULTS: Collapsed across one-legged and two-legged conditions, patellofemoral joint force and stress were significantly greater (p < 0.01) in floor squat than BOSU-ball squat at 40°, 50°, and 70° knee angles during squat descent and at 60° and 50° knee angles during squat ascent. Collapsed across BOSU-ball squat and floor squat, patellofemoral joint force and stress were significantly greater (p < 0.01) for one-legged squat than two-legged squat during all knee angles. Significant interactions (p < 0.01) were found at 30°, 40°, 50°, 60°, and100° knee angles during squat descent, and at 100°, 90°, 80°, and 70° knee angles during squat ascent. Patellofemoral joint force and stress were significantly greater (p < 0.01) in two-legged floor squat than two-legged BOSU-ball squat, but no differences were found between one-legged floor squat and one-legged BOSU-ball squat. CONCLUSIONS: Squatting progression employing lower to higher patellofemoral loading over time during patellofemoral pain rehabilitation may proceed as follows: 1) two-legged BOSU-ball squats at lower more functional knee angles (0°-50°); 2) two-legged floor squats at lower more functional knee angles (0°-50°); 3) one-legged BOSU-ball and floor squats at lower more functional knee angles (0°-50°); 4) two-legged BOSU-ball squats at lower and higher knee angles (0°-100°); 5) two-legged floor squats at lower and higher knee angles (0°-100°); 6) one-legged BOSU-ball and floor squats at lower and higher knee angles (0°-100°).