Familial inheritance of osteoarthritis: documented family subsets.

Identifying susceptibility genes for a common complex disease is complicated by heterogeneity at several levels including allelic, locus, clinical, and population. The latter two can be alleviated by focusing on particular subsets of families that have well-defined disease. For osteoarthritis it was commonly thought that a generalized disease approach was the wisest ascertainment because this would target a systemic disease that had to have a major genetic component. However, this intuitive idea has not yet provided the breakthroughs many expected and it has become apparent that a joint-specific and gender-specific approach may be more fruitful. Large collections of osteoarthritis cohorts have been assembled either as part of prospective studies or more directly. Some of these collections have targeted specific joints, others have not. The latter are, however, amenable to stratification. Many collectors included the acquisition of DNA as a core study aim. A variety of osteoarthritis subsets are therefore available for genetic analysis. Open accessibility is another matter. Although many collections were funded partly or wholly by public or charitable organizations, they can be jealously guarded or have arcane access rights. Open access, with necessary safeguards, is something the osteoarthritis research community should strive for if progress toward susceptibility gene identification is to be swift.