The ratio between the serum and knee synovial fluid (SF) adipokine level has been correlated to osteoarthritis (OA) severity. No study has examined the relative concentration of adipokines in shoulder OA. However, in this study, we document serum and SF concentrations, and serum/SF ratios, of leptin and adiponectin among individuals with end stage shoulder OA, and compare ratios with a sample of individuals with end stage knee OA.
Thirty-five patients with end stage knee and shoulder OA were surveyed prior to surgery for demographic data and body mass index (BMI). Synovial fluid (SF) and serum samples were analyzed for leptin and adiponectin. Serum/SF ratios were calculated and compared across cohorts.
Knee and shoulder cohorts were matched, without clinical differences for age, gender, and BMI. Serum and SF leptin levels are consistently higher in knee OA patients as compared to shoulder OA patients. Further, serum/SF adiponectin ratios are greater than that for leptin across both joints.
Our findings may help, in part, explain the findings that obesity has a stronger association to knee OA than shoulder OA. Whether this reflects a difference in local production of adipokines, capsular permeability, or both must be further studied.