Occupational activity and the risk of hip osteoarthritis.

Osteoarthritis is probably the most common joint disorder in the world. In western populations, radiographic evidence of osteoarthritis occurs in the majority of people by the age of 65 years, and in about 80% of those aged 75 years and above.' The disorder is second only to ischaemic heart disease as a cause of work related disability in men over 50 years of age, and accounts for more hospital admissions than rheumatoid arthritis each year. Osteoarthritis is defined as focal loss of articular cartilage with variable subchondral bone reaction. There is incomplete concordance between these pathological features and radiographic or clinical characteristics of the disorder. However, the difficulties encountered in using a pathological definition for epidemiological studies of osteoarthritis have led to the widespread use of radiological and clinical markers. The radiographic features conventionally used to define disease severity include joint space narrowing, osteophytes, subchondral sclerosis, cyst formation, and abnormalities of bony contour. These radiographic features can be incorporated in rating scales at the commonly affected joint sites (for example the hand, knee, and hip) permitting standardisation of disease severity.2 The two clinical sequelae of osteoarthritis which are most relevant to epidemiological studies are joint pain and functional impairment. The development of osteoarthritis at any joint site depends upon a generalised predisposition to the condition, and abnormalities of biomechanical loading which act at specific joints.'3 Individual risk factors which may be associated with a generalised susceptibility to the disorder including obesity, a family history, and hypermobility. Those which reflect local biomechanical insults include trauma, abnormalities of joint shape, and physical activity. In this review we shall focus on the relation between occupational physical activity and the risk of osteoarthritis of the hip.