Design and Evaluation of an Offloading Orthosis for Medial Knee Osteoarthritis

Abstract

Knee osteoarthritis is an incurable degenerative joint disease that affects millions of people in Canada. Characterized by stiffness and knee pain in the early stages, it can cause loss of function and mobility. Most treatment options are either not sustainable, such as pain medications and steroid injections, or invasive, such as knee replacement surgery. While therapeutic options, such as physiotherapy, have been shown to have a positive effect on pain and activity levels over time, minimal immediate relief has been observed. Moreover, these treatments or combinations of treatments can be costly. Alternatively, offloading knee orthoses are a cost-effective option that provides immediate pain relief when worn. Offloading knee orthoses, however, have low patient compliance rates. To improve patient compliance and optimize patient benefit, current orthosis designs must be enhanced to improve comfort, increase the perceived effect and be adjustable to the patient. Consequently, this thesis presents the design, fabrication and testing of an offloading knee orthosis joint designed to enhance comfort and perceived effect. This improvement is achieved by developing a novel modular orthosis that features an offloading mechanism intended to relieve the load on the joint through an offloading moment solely during stance phase and reduce the moment during swing phase when offloading is not needed. The evaluation of the proposed orthosis design was achieved by fabricating an experimental prototype and performing mechanical testing. Three-point bending tests demonstrated a generated offloading moment of 3.36 Nm, creating a noticeable offloading effect during stance, and reduced the moment to less than 0.5 Nm after 35° of knee flexion, thus, increasing comfort during swing phase and sitting when offloading forces are not needed.