Defining hip pain for population studies.

BACKGROUND Identifying pain as coming from the hip joint is more complex than for other large joint sites. There is no accepted best approach to defining hip pain for use in clinical and epidemiological studies. OBJECTIVE To compare the use of verbal and pictorial descriptions in ascertaining hip pain. METHODS A cross sectional population based study on 2935 subjects compared groups reporting hip pain either using a pain diagram, or answering a question specifically asking about hip pain. The groups were compared with a group reporting no pain for various clinical indices of hip disease, including limitation of range of movement and evidence of radiographic change. RESULTS Subjects who satisfied both criteria for hip pain were substantially more likely to have used analgesics, consulted a physician, or had walking difficulty. Differences in range of movement were less clear cut but radiographic damage was more evident in those with both criteria. CONCLUSIONS Subjects whose pain satisfies both a pictorial and a verbal definition (where the patient uses the word "hip") have the strongest relation to indicators of hip disease. This approach is recommended when a specific definition is required for ascertaining individuals for study.