Neuromuscular adaptations related to medial knee osteoarthritis and influence of unloader braces on neuromuscular activity in knee OA subjects – A systematic review

Unloader braces are a treatment modality for medial compartment knee osteoarthritis (MC-KOA). The functional mechanisms involved are not yet fully understood. Therefore, this two-part systematic review (SR) examines the following research questions: How is muscle activation altered by MC-KOA, and do MC unloader braces alter muscle activation? If so, could this alteration be part of the unloading mechanism by affecting the altered muscle activity in MC-KOA?
A systematic literature search was conducted using PubMed, LIVIVO, Web of Science, Google Scholar, and CENTRAL for articles published until August 2023. The first SR, examining neuromuscular alterations, identified 703 articles, with a final inclusion of 20. The second SR, which evaluated the neuromuscular effects of unloader braces, identified 123 articles with the final inclusion of 3. Individuals with MC-KOA demonstrated increased activity and co-contraction of the periarticular knee muscles, whereas MC unloader braces seemed to reduce activity and co-contraction. In contrast to the belief that unloader braces result in muscle weakness as they decrease muscle activity and co-contraction, our limited insights indicate that they rather might reduce the pathological increase. This may result in joint load reduction owing to lower compressive forces. However, further investigation is required.