Extensive joint hypermobility, lower serum cartilage oligomeric matrix protein (COMP) levels, and early-onset osteoarthritis (OA) are phenotypes of inherited pseudoachondroplasia and multiple epiphyseal dysplasia. However, few studies have evaluated the association between articular hypermobility and primary OA. We undertook the present study to evaluate this association and to test the hypothesis that COMP levels are associated with hypermobility in patients with OA and individuals without OA.
Two separate cohorts were available for analysis, the CARRIAGE (CARolinas Region Interaction of Aging Genes and Environment) extended family and a subset of the GOGO (Genetics of Generalized Osteoarthritis) sibpair cohort. In the CARRIAGE family, we performed hand and knee examinations and hypermobility evaluations (Beighton criteria) and obtained sera for measurement of COMP and hyaluronan (HA). Data on COMP and HA levels and extensive joint radiographic and hypermobility data were also available for the GOGO cohort.
The prevalence of hypermobility was 13% in the CARRIAGE family and 5% in the GOGO cohort. In the CARRIAGE family, hypermobility was associated with a significantly reduced prevalence of hand (especially proximal interphalangeal joint) and knee OA and lower mean serum COMP levels, both in the total cohort and in non-hand-OA subgroups. These results were further validated in the GOGO subsets without radiographic OA, in which hypermobility was also associated with a significantly reduced mean serum COMP level (P < 0.0001 adjusted for age). Serum HA levels did not differ in relation to hypermobility in either cohort.
The present results indicate that there is an inverse relationship between hypermobility and hand and knee OA, and that hypermobility is associated with lower serum COMP levels. Genetic variations of the COMP gene may account for some subgroups of benign joint hypermobility.