An Analysis of Potential Sex Differences in Knee Osteoarthritis

The goal of this study is to determine if sex differences can be identified in the knee joint that can contribute to the differences in incidence and severity of knee osteoarthritis observed in men and women, particularly over the age of 50. Recent studies assessing the responses of articular chondrocytes to systemic factors suggest that there are underlying differences in the biochemical and molecular characteristics of male and female cells. It is also known that immune responses differ in males and females, suggesting that there may be important differences in the levels of immune modulators in the joint tissues, including the synovial membrane, the synovial fluid, and the cartilage itself. Responses to the vitamin D metabolite 1_,25(OH)2D3 are upregulated in osteoarthritic cartilage, raising the possibility that males and females differ in their circulating levels of vitamin D, in the content of vitamin D metabolites in the synovial tissues, or in the ability of the cells to respond to this steroid. Similarly, in post-menopausal women, circulating estrogen is reduced relative to testosterone, but it is not known if this might impact the knee. Most importantly, it is not known if potential sex differences can be correlated with severity of disease.

This study is based on the hypothesis that sex differences exist in different tissues of the knee joint, which contribute to the increased incidence and severity of knee osteoarthritis in older women as compared to older men.

To test this hypothesis, the investigators will use tissues and fluids that are normally discarded during the course of total knee replacement surgery to investigate potential sex differences.