Limb Underloading in Walking Transmits Less Dynamic Knee Joint Contact Forces after Anterior Cruciate Ligament Reconstruction

INTRODUCTION: Individuals with anterior cruciate ligament reconstruction (ACLR) often walk with a less dynamic vertical ground reaction force (vGRF), exemplified by a reduced first peak vGRF and elevated midstance vGRF compared with uninjured controls. However, the mechanism by which altered limb loading affects actual tibial plateau contact forces during walking remains unclear. METHODS: Our purpose was to use musculoskeletal simulation to evaluate the effects of first peak vGRF biofeedback on bilateral tibiofemoral contact forces relevant to the development of post-traumatic osteoarthritis in 20 individuals with ACLR. We hypothesized that reduced first peak vGRF would produce less dynamic tibial plateau contact forces during walking in individuals with ACLR. RESULTS: As the pivotal outcome from this study, and in support of our hypothesis, we found that less dynamic vGRF profiles in individuals with ACLR-observations that have associated in prior studies with more cartilage breakdown serum biomarkers and reduced proteoglycan density-are accompanied by less dynamic tibiofemoral joint contact forces during walking. CONCLUSION: We conclude that more sustained limb-level loading, a phenotype that associates with worse knee joint health outcomes after ACLR and was prescribed herein using biofeedback, alters the loading profile and magnitude of force applied to tibiofemoral cartilage.