A Heritable Predisposition to Osteoarthritis of the Hip.

Using THA as a proxy for underlying osteoarthritis, we describe population-based familial clustering of osteoarthritis of the hip. The GIF test for excess relatedness on 1049 patients that underwent THA (and do not have a diagnostic code for other conditions leading to THA) showed excess relatedness (P<0.001). Even when close relationships were ignored (closer than third-degree relationships), excess relatedness was observed (P=0.020). Relative risk was elevated in first-degree (RR 2.59; 95% CI 1.84-3.53, P=2.0e(-7)), second-degree (RR 1.66; 95% CI 1.11-2.39; P=0.0075) and third-degree relatives (RR 1.46; 95% CI 1.17-1.81; P=5.7e(-4)). Excess relatedness of individuals who had undergone THA for osteoarthritis and elevated risks to both near and distant relatives were observed.