The study project aims at examining molecular markers in synovial fluid, bone and articular cartilage from osteoarthritic thumb basal joints. The degradation of extracellular matrix (ECM) proteins in thumb basal joints will be evaluated in association to the metabolic profile of the patient, but we also aim to compare the ECM degradation and inflammatory profiles with articular cartilage degradation ECM profile from knee joints with osteoarthritis. A third aim is to evaluate associations between patient-reported hand function, pain, strength and range of thumb motion to analyses of synovial fluid.