Wnt signalling plays an important role in bone and cartilage metabolism. Activation of Wnt signalling promotes bone formation but cartilage degradation. Sclerostin (SOST) can inhibit Wnt signalling. It is expressed by chondrocytes in the articular cartilage and osteocytes in the subchondral bone. Since osteoarthritis (OA) is a joint degenerative disease involving both bone and joint compartments, SOST may have a role in mediating the progression of this disease. This review examined the current literature on the role of SOST in the pathogenesis of OA and its usefulness as a biomarker of OA. Most studies agree that SOST is upregulated as a rescue mechanism in OA to prevent further degenerative changes of the joint. It antagonises inflammation-induced cartilage catabolism while preserving chondrocyte anabolic activities. It also prevents abnormal bone mineralisation and osteophyte formation. However, studies on the performance of SOST as a biomarker to detect and stage OA are limited. Further studies are required to determine whether SOST can be a biomarker or therapeutic target for OA.