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From a retrospective, cohort study of 205 patients diagnosed with full-thickness tears of the rotator cuff, we determined, using ultrasound, the prevalence of such tears in their 129 siblings. Using 150 spouses as controls, the relative risk of full-thickness tears in siblings versus controls was 2.42 (95% CI 1.77 to 3.31). The relative risk of symptomatic fullthickness tears in siblings versus controls was 4.65 (95% CI 2.42 to 8.63).The significantly increased risk for tears in siblings implies that genetic factors play a major role in the development of full-thickness tears of the rotator cuff.In the UK the shoulder is the third commonest site of musculoskeletal disease (16%) after the spine and knee (23% and 19%, respectively) 1 as well as being the third most common reason for orthopaedic referral in the USA (7.9%) after the knee and spine (14.9% and 8.2%, respectively). 2 Full-thickness tears of the rotator cuff are among the most frequently encountered causes of pain and dysfunction in the shoulder. 3 Estimates for the prevalence of full-thickness tears vary widely. Most cadaver studies give a prevalence of 20%, 4 but estimates of 5% to 30% 5,6 have been published. In asymptomatic individuals estimates of prevalence of 15% to 23.4% have been described after investigation by MRI 7 and ultrasound. 8 All studies agree that the prevalence increases with age and that its associated morbidity, in terms of pain and loss of function, can be severely debilitating. Pain in the shoulder is a common cause of absenteeism from work and is a burden on medical resources. 9 Reported estimates for the mean cost of repair of a rotator cuff vary from US$ 9444 10 to US$ 25 870 11 with a mean time off work of seven months.Theories regarding the causes of full-thickness tears are varied. Historically, mechanical compression of the tendons of the cuff was thought to be the initiating factor. Acromial morphology and the presence of spurs, the morphology of the coracohumeral ligament and the presence of osteophytes at the acromioclavicular joint were all considered to be relevant, although, as early as 1934, Codman 12 favoured an intrinsic theory of degeneration of the tendons of the cuff. Current opinion favours a combination of repetitive microtrauma in association with age-related degenerative changes within the tendons. There is a lack of understanding as to what causes pain in a full-thickness tear and why symptoms are so variable.Increasingly, such tears are being regarded as a normal consequence of the ageing process. 8,13 No studies to date have addressed a possible genetic basis for their pathogenesis and symptomatology. We therefore describe the results of a prospective, cross-sectional study of patients with full-thickness tears. Our aim was to establish the relative risk of their development as well as the risk of occurrence of symptomatic tears in siblings of patients with tears which had been diagnosed by ultrasound. Patients and MethodsComputerised hospital records were used to identify all patients who had been diag...

We present a two-stage genomewide scan for osteoarthritis-susceptibility loci, using 481 families that each contain at least one affected sibling pair. The first stage, with 272 microsatellite markers and 297 families, involved a sparse map covering 23 chromosomes at intervals of approximately 15 cM. Sixteen markers that showed evidence of linkage at nominal P

Chromosome 2q is likely to contain at least one susceptibility locus for OA.

Our data suggest the importance of a constitutional tendency to idiopathic, end-stage OA, a disorder traditionally associated with environmental factors leading to 'wear and tear'.

COL9A1 may therefore be a susceptibility locus for female hip OA. In addition, there was weak evidence of linkage to HLA/COL11A2 (6p21.3) in female hip OA with a corrected P-value of 0.016.

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From a prospective, cross-sectional survey of 402 patients who had a total hip (THR) or a total knee (TKR) replacement for idiopathic osteoarthritis (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 spouses 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 siblings and spouses over 64 years of age were compared. Using a threshold liability model (Falconer), the heritability of end-stage OA of the hip 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.