GENETIC INFLUENCES IN END-STAGE OSTEOARTHRITIS - SIBLING RISKS OF HIPAND KNEE REPLACEMENT FOR IDIOPATHIC OSTEOARTHRITIS

From a prospective, cross-sectional survey of 402 patients who had a t otal hip (THR) or a total knee (TKR) replacement for idiopathic osteoa rthritis (OA) at a major centre, we determined the prevalence of these replacements for idiopathic OA in their 1171 siblings and 376 spouses . Using spouses as controls, the relative risk of THR in siblings was 1.86 (95% CI 0.93 to 3.69). The relative risk for TKR in siblings v sp ouses was 4.8 (95% CI 0.64 to 36.4) whereas the risk for the combined outcome measure of THR or TKR was 2.32 (95% CI 1.22 to 4.43) when sibl ings and spouses over 64 years of age were compared. Using a threshold liability model (Falconer), the heritability of end-stage OA of the h ip was estimated at 27%. The increased risks of joint replacement for severe, idiopathic OA which we found in siblings suggest that genetic influences are important in end-stage OA of the hip and knee.