Patellofemoral Joint Loading During the Performance of the Forward and Side Lunge with Step Height Variations

BACKGROUND: Forward and side lunge exercises strengthen hip and thigh musculature, enhance patellofemoral joint stability, and are commonly used during patellofemoral rehabilitation and training for sport. HYPOTHESIS/PURPOSE: The purpose was to quantify, via calculated estimates, patellofemoral force and stress between two lunge type variations (forward lunge versus side lunge) and between two step height variations (ground level versus 10 cm platform). The hypotheses were that patellofemoral force and stress would be greater at all knee angles performing the bodyweight side lunge compared to the bodyweight forward lunge, and greater when performing the forward and side lunge at ground level compared to up a 10cm platform. STUDY DESIGN: Controlled laboratory biomechanics repeated measures, counterbalanced design. METHODS: Sixteen participants performed a forward and side lunge at ground level and up a 10cm platform. Electromyographic, ground reaction force, and kinematic variables were collected and input into a biomechanical optimization model, and patellofemoral joint force and stress were calculated as a function of knee angle during the lunge descent and ascent and assessed with a repeated measures 2-way ANOVA (p<0.05). RESULTS: At 10° (p=0.003) knee angle (0° = full knee extension) during lunge descent and 10° and 30° (p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in forward lunge than side lunge. At 40°(p=0.005), 50°(p=0.002), 60°(p<0.001), 70°(p=0.006), 80°(p=0.005), 90°(p=0.002), and 100°(p<0.001) knee angles during lunge descent and 50°(p=0.002), 60°(p<0.001), 70°(p<0.001), 80°(p<0.001), and 90°(p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in side lunge than forward lunge. At 60°(p=0.009) knee angle during lunge descent and 40°(p=0.008), 50°(p=0.009), and 60°(p=0.007) knee angles during lunge ascent patellofemoral joint force and stress were greater lunging at ground level than up a 10cm platform. CONCLUSIONS: Patellofemoral joint loading changed according to lunge type, step height, and knee angle. Patellofemoral compressive force and stress were greater while lunging at ground level compared to lunging up to a 10 cm platform between 40° - 60° knee angles, and greater while performing the side lunge compared to the forward lunge between 40° - 100° knee angles. LEVEL OF EVIDENCE: II