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Osteoarthritis 1: Physiology, risk factors and causes of pain.

Osteoarthritis (OA) is a synovial joint disorder characterised by pain, stiffness, and restricted function. It is often classed as a degenerative disease because the affected joints deteriorate over time. This article, the first in a three-part series, describes the complex pathophysiology and causes of pain in OA, risk factors, and how it is diagnosed.