Objective: To determine whether a polymorphism of the vitamin D receptor (VDR) gene, already associated with osteoporosis, might also relate to the risk of osteoarthritis (OA).
Methods: A population cohort of 351 postmenopausal women (ages 45-64 years) was studied using anteroposterior radiographs of the knee, which were graded for OA according to the Kellgren and Lawrence classification system. The VDR genotype was determined by using polymerase chain reaction and by digestion with the restriction enzyme Taq I.
Results: The VDR allele "T" was associated with an increased risk of knee OA compared with the "t" allele, with an odds ratio of 2.82 (95% confidence interval 1.16-6.85; P = 0.02). A dominant pattern of risk was suggested. The frequency of the VDR genotype differed significantly between OA cases and controls (P = 0.03 by Fisher's exact test).
Conclusion: A Taq I polymorphism of the VDR gene appears to be associated with an increased risk of knee OA. This is the first genetic locus that has been shown to influence the risk of early knee OA within the general population.