THE HEREDITARY PREDISPOSITION TO HIP 1 OSTEOARTHRITIS AND ITS ASSOCIATION 2 WITH ABNORMAL JOINT MORPHOLOGY Hereditary

Objective: Genetic factors and abnormalities of joint morphology are important in the aetiology of hip 32 OA. The extent to which genetic influences are manifest through joint morphology has undergone 33 limited investigation. Using a cohort with an hereditary predisposition to end-stage hip OA and a 34 control group with no inherited risk, we aimed to identify associations with abnormal joint 35 morphology and clinical features. 36 37 Design: 123 individuals (mean age 52 years) with a family history of THA (termed ‘sibkids’) were 38 compared with 80 spouse controls. Morphology was assessed using standardised radiographs and 39 cam, dysplasia, and pincer deformities defined. Regression modelling described the association of 40 cohort with abnormal joint morphology, adjusting for confounders (age, gender, BMI, OA, and 41 osteophyte). 42 43 Results: Sibkids had an odds ratio of 2.1 (95%CI 1.3-3.5) for cam deformity. There were no 44 differences in the prevalence of dysplasia or pincer deformities. In both groups, hips with cam 45 deformities or dysplasia were more likely to have clinical features than normal hips (OR 4.46 (1.8- 46 11.3), and 4.40 (1.4-14.3) respectively). Pincer deformity was associated with positive signs in the 47 sibkids but not in the controls (OR 3.0; 1.1-8.2). 48 49 Discussion: After adjustment for confounders that cause secondary morphological change, individuals 50 with an hereditary predisposition to end-stage hip OA had a higher prevalence of morphological 51 abnormalities associated with hip OA. Sibkids were more likely to demonstrate clinical features in the 52 presence of pincer deformity, suggesting that the genes are acting not only through abnormal 53 morphology but also through other factors that influence the prevalence of pain.