Reduction of knee loading during landing and cutting with a dual-joint brace

Non-contact ACL injuries pose a serious threat to athletes, often leading to high medical costs and long-term disability. Conventional knee braces have not been effective in reducing knee loading associated with these injuries. This study introduces a novel hip-knee brace (HKB) that harnesses the biomechanical advantage of proximal joint adjustment by applying tension through embedded elastic fabric, thereby facilitating increased hip flexion and reducing stress on the knee. Simulations in OpenSim indicated that an axial deformation-tension of approximately 3 N/mm was optimal for achieving a 3° increase in hip flexion. Twelve participants performed single-leg landing and 90° cutting tasks under three conditions: no brace, a commercial sleeve, and our HKB. Wearing the HKB significantly increased hip flexion angles (by 5.8° during landing and 3.8° during cutting) and reduced knee extensor moments (by 0.022 BW × BH and 0.015 BW × BH, respectively) while raising the hamstring-to-quadriceps activation ratio. These findings suggest that by promoting greater hip flexion and enhanced neuromuscular control, the dual-joint HKB can help minimize knee loads and reduce the risk of noncontact ACL injuries.