Thumb base osteoarthritis: A hand osteoarthritis subset requiring a distinct approach.

Hand osteoarthritis (OA) is usually a polyarticular disease, preferentially affecting the thumb base (TB) and interphalangeal joints. TB OA alone is generally not addressed separately, but as a part of hand OA. Studies have shown that OA in the TB joints clusters together, as does OA in the interphalangeal joints, supporting it as a distinct subset. Further support for this view comes from a specific risk profile, influence on clinical burden, impact of synovial inflammation on local joint pain, and specific treatment interventions. Therefore, clinical care and future hand OA research should not only address hand OA in general but also should focus on the different subsets separately, including TB OA.