Spring Back: A Musculoskeletal Modeling Investigation of Contact Loading and Kinematics During Bilateral Knee Bracing
Osteoarthritis affects roughly 270 million people worldwide, and the number of total knee arthroplasty surgeries in the year 2010 alone was 4.7 million. Surgery is not feasible for all patients with osteoarthritis, therefore optimization of knee braces for the mitigation and prevention of OA is being investigated. Further analysis of the kinematic and kinetic effects of knee bracing must be obtained to enhance current designs. Knee joint contact loads are a primary factor in the development of knee osteoarthritis. Lower contact loads are healthier on the knee joint, and braces are designed to reduce this contact load. One way to investigate the effects of bracing efficiently is through musculoskeletal modeling to provide estimates of contact loading at the knee. In this study, a novel spring-based knee extension assist external brace was analyzed to determine how knee contact forces are altered during different activities of daily living including deep knee flexion tasks such as: squatting and stair ascent/descent. A generic musculoskeletal model was adapted for knee bracing and anatomical subject-specificity. Although not significant (p>0.15), this novel tri-compartmental unloader was estimated to reduce contact loading at the tibiofemoral (p=0.18) and patellofemoral (p=0.16) joints during squatting and gait trials, (14%, 16.5%, respectively) with higher effects on the medial compartment. Knee flexion angle was significantly reduced by 22% and 10% for gait and squatting trials, respectively (p<0.05), along with significantly slower cycle times for each trial when braced (p<0.05). These finding may indicate that knee braces and their effectiveness of reducing contact load can be dynamically modified to change kinematics to be more effective during different activities of daily living.