Is the association between knee injury and knee osteoarthritis modified by the presence of general joint hypermobility?

OBJECTIVE: To evaluate whether joint hypermobility modifies the association between knee joint injury and knee osteoarthritis (OA) among adults. METHODS: Data were from three studies: Genetics of Generalized Osteoarthritis (GOGO; N = 2341), Genetics of Osteoarthritis (GO; N = 1872), and the population-based Johnston County Osteoarthritis Project (JoCoOA; N = 1937). Knee injury was defined as a self-report of prior fracture or severe injury to either knee. OA was defined using three variables: knee pain (pain, aching, or stiffness of the knee on most days), radiographic OA (rOA; Kellgren-Lawrence grade 2–4), and symptomatic OA (sxOA; knee rOA with knee pain). Joint hypermobility was defined as Beighton score ≥4. For each study, separate logistic regression models, stratified by joint hypermobility, were used to estimate the association of knee injury with knee pain, rOA, and sxOA, adjusting for age, sex, body mass index, and race (JoCoOA only); statistical interactions between injury and hypermobility were assessed (p-value<0.10). RESULTS: In all three studies, knee injury was associated with OA variables of knee pain, rOA, and sxOA (adjusted odds ratios [aOR] range 1.83–3.75). The association of knee injury with rOA and sxOA was magnified among individuals with vs. without joint hypermobility in GOGO: rOA aOR 11.0, 95% confidence interval [CI] 4.0–30.1 vs. 2.7, 95% CI 2.0–3.6, p = 0.009; sxOA aOR 9.2, 95% CI 3.5–24.3 vs. 3.3, 95% CI 2.4–4.4, p = 0.032. Interactions were not statistically significant in GO or JoCoOA. CONCLUSIONS: In a general adult population, the presence of joint hypermobility may not modify the strong association between knee injury and OA.