The symptoms of osteoarthritis and the genesis of pain.

Symptomatic osteoarthritis (OA) causes substantial physical and psychosocial disability. This article delineates the characteristic symptoms and signs associated with OA and how they can be used to make the clinical diagnosis. The predominant symptom in most patients is pain. The remainder of the article focuses on what is known about the causes of pain in OA and factors that contribute to its severity. Much has been learned during recent years, but much of this puzzle remains unexplored or inadequately understood.