Assessment of a genetic contribution to osteoarthritis of the hip: sibling study.

OBJECTIVES To study the influence of genetics on the development of hip osteoarthritis as determined by structural change on plain radiographs. DESIGN Sibling study. SETTING Nottinghamshire, England. PARTICIPANTS 392 index participants with hip osteoarthritis of sufficient severity to warrant total hip replacement, 604 siblings of the index participants, and 1718 participants who had undergone intravenous urography. MAIN OUTCOME MEASURE Odds ratios for hip osteoarthritis in siblings. RESULTS The age adjusted odds ratios in siblings were 4.9 (95% confidence interval, 3.9 to 6.4) for probable hip osteoarthritis and 6.4 (4.5 to 9.1) for definite hip osteoarthritis. These values were not significantly altered by adjusting for other risk factors. CONCLUSION Siblings have a high risk of hip osteoarthritis as shown by structural changes on plain radiographs. One explanation is that hip osteoarthritis is under strong genetic influence.