Trunk and Shank Position Influences Patellofemoral Joint Stress in the Lead and Trail Limbs During the Forward Lunge Exercise

STUDY DESIGN: Controlled laboratory study, repeated-measures design. BACKGROUND:The effects of trunk and shank position on patellofemoral joint stress of the lead limb have been well studied; however, the effects on the trail limb are not well understood. OBJECTIVES: To test the hypothesis that trunk and shank position may influence patellofemoral joint stress in both limbs during the forward lunge exercise. METHODS: Patellofemoral kinetics were quantified from 18 healthy participants performing the lunge exercise with different combinations of trunk and shank positions (vertical or forward). A 2-by-3 (limb-by-lunge variation) repeated measures analysis of variance was performed, using paired t tests for post hoc comparisons. RESULTS: The trail limb experienced greater total patellofemoral joint stress relative to the lead limb, regardless of trunk and shank position (P<.0001). The lunge variation with a vertical shank position resulted in significantly greater peak patellofemoral joint stress in the trail limb relative to the lead limb (P<.0001). A forward trunk and shank position resulted in the highest patellofemoral stress in the lead limb (P<.0001). CONCLUSION: Trunk and shank positions have a significant influence on patellofemoral joint loading of both limbs during the forward lunge, with the trail limb generally experiencing greater total joint stress. Restricting forward translation of the lead-limb shank may reduce patellofemoral joint stress at the expense of increased stress in the trail limb. Technique recommendations should consider the demands imposed on both knees during this exercise.