Is early osteoarthritis associated with differences in joint congruence?

Previous studies suggest that osteoarthritis (OA) is related to abnormal or excessive articular contact stress. The peak pressure resulting from an applied load is determined by many factors, among which shape and relative position and orientation of the articulating surfaces or, referring to a more common nomenclature, joint congruence. It has been hypothesized that anatomical differences may be among the causes of OA. Individuals with less congruent joints develop higher peak pressure and thus are more exposed to the risk of OA onset. The aim of this work is to verify if any relation exists between joint congruence and the early onset of OA or its higher incidence within the female population, with specific regards to the articulation of the first carpometacarpal (CMC) joint. 59 asymptomatic and 38 patients with early OA were CT-scanned with their dominant or arthritic hand in a neutral configuration. The adopted measure of joint congruence, for its definition, is size dependent. For this reason, joint congruence was also normalized with respect to the size of the joint. Two-way ANOVAs were used to determine the correlation of joint congruence with pathology and sex both before and after normalization. We found a significant correlation between joint congruence and sex due to the sex-related differences in size. In fact, the observed correlation disappeared after normalization. Although joint congruence increased with size, it did not correlate significantly with the onset of OA. Differences in joint congruence do not seem to be among the causes of OA onset or predisposition.