Pain is the commonest symptom of osteoarthritis (OA), the principal reason why individuals seek medical care and a major determinant of other outcomes such as disability and joint replacement. Most studies have examined knee OA: little is known about other sites. Community studies indicate only a modest relationship between structural change on X-ray and reporting of pain. Many community subjects, for example, fail to complain of pain despite extensive X-ray change, while others report pain with normal X-rays. Pain severity of patients attending hospital is even less related to X-ray change, being more dependent on body mass index (BMI), coping strategies and psychosocial variables. Many patients can identify more than one type of pain. It is increasingly clear that OA pain is heterogeneous, being classifiable on the basis of location, precipitating factors, response to anti-inflammatory and steroid medication and the effects of local anaesthetic. This potential to classify OA pain represents a useful tool with which to test hypotheses regarding structural origin of pain.