A biomechanical analysis of a medial unloading brace for osteoarthritis in the knee

Objectives. The goals of the study were to measure the force applied to the lateral side of the knee by a valgus loading brace designed for patients with medial compartment osteoarthritis (OA) and to compare the varus moment at the knee during level gait with and without the brace. Methods. Five subjects diagnosed with medial compartment OA were fitted with a custom Monarch valgus loading knee brace. A 3-dimensional video-based motion analysis system and force plate information were used to calculate forces and moments at the knee. An instrumented condylar bladder was used to determine the force applied to the knee by the brace. The varus moments for the braced and unbraced trials were compared during gait at 15%, 20%, 25%, and 30% of stance. Results. The Monarch brace significantly reduced the varus moment at 20% and 25% of stance. The valgus force measured with the custom condylar bladder remained fairly constant through out the first 80% of the stance phase. Conclusions. The reduced varus moment observed for the braced condition demonstrates the biomechanical function of the brace in 5 subjects and may contribute to a reduction of pain for patients with medial compartment OA.