Risk factors for osteoarthritis (OA) in the different compartments of the knee are important in the pathogenesis of knee OA. We examined the risk factors associated with OA of the tibiofemoral and patellofemoral compartments of the knee.
A population-based study of 325 unrelated, middle aged females was performed. Knee and hand radiographs for each individual were graded for joint space narrowing and osteophytes using a standard atlas. Individuals with knee OA were classified as having tibiofemoral OA only, patellofemoral OA only, or a combination of both tibiofemoral and patellofemoral OA. Information on risk factors was obtained by a structured interview and examination.
Obesity was associated with all the categories of knee OA. This relationship was strongest for the combined tibiofemoral and patellofemoral OA [OR (95% CI) = 7.26 (2.36-22.31) for the highest vs lowest third]. There was a strong association between distal interphalangeal OA and isolated tibiofemoral OA [OR = 6.67 (1.94-22.94)], but no association with patellofemoral OA. There was an inverse association between premenopausal status and patellofemoral OA [OR = 0.23 (0.06-0.84)].
The pathogenetic mechanisms involved in patellofemoral and tibiofemoral OA may differ; clarification of the etiology of OA for the separate compartments of the knee is needed.