Required Knee Flexion Moment for Medial Unloader Knee Brace in Medial Compartment Osteoarthritis

Abstract

Medial unloader braces are often developed to achieve pain elimination of the knee medial compartment. In order to prevent bone-bone contact in the knee joint, a new mechanism is designed to unload the knee based on a novel computational procedure for the first time. As the knee flexion-extension moment has a high impact on tibiofemoral contact force, we use the procedure that calculates the cartilage penetration depth and the force in the patellar tendon simultaneously which are the main parameter for applying computational knee flexion-extension torque. Therefore, the new unloader brace applies computational knee flexion-extension torque, then it decreases the penetration depth by the novel brace to eliminate pain in knee osteoarthritis. We calculate the instantaneous center of rotation of the knee and design a new flexion hinge for tracking the desired instantaneous center of rotation reducing unwanted forces. The novel brace flexion hinge tracks the instantaneous center of rotation accurately. Moreover, the flexible cord is designed to apply extension torque. It concluded that the 36.25 Nm of the extension moment leads to 0.3 mm cartilage penetration depth reduction. The embedded mechanism applies knee extension moment by the flexible cord to support assistive extension moment with the maximum amount of 1375 N. Finally, by computing the magnitude of knee flexion-extension torque, we know the relation between compensated moment applied by the brace and tibiofemoral contact force reduction for the first time.