Serum hyaluronan levels increase with the total number of osteoarthritic joints and are strongly associated with the presence of knee and finger osteoarthritis

Although serum hyaluronan (HA) levels increase in patients with osteoarthritis (OA), the association between OA severity and elevation of serum HA levels is not clear. Our purpose was to investigate the relationship between serum HA levels and OA in various anatomical sites and to detect which joints are strongly correlated with elevated serum HA levels. Seven hundred and ten individuals from the general population who participated in the Iwaki Health Promotion Project in 2008 were involved. Kellgren-Lawrence grade 2 or higher in the knee, hip, lumbar spine, finger and wrist was defined as OA. Serum HA levels were determined on the same day. Spearman's correlation coefficients between serum HA levels and total number of joints affected by OA were calculated. Linear regression was analysed with serum HA levels as the independent variable; age, gender, presence of OA and intake of supplements were used as dependent variables. Prevalence of knee OA was 30.7 %, hip 16.8 %, lumbar spine 65.1 %, wrist 9.0 % and finger 22.0 %. Serum HA levels had a positive correlation with the number of involved joints, and the correlation coefficient was 0.410 (p < 0.001). Serum HA was significantly affected by age (beta = 0.382), knee OA (beta = 0.163) and finger OA (beta = 0.164). Although this biomarker reflects a systemic condition, higher serum HA levels were associated with total number of OA joints. Knee and finger OA were key joints related to increased serum HA levels. These results are valuable in understanding characteristics of serum HA levels as a biomarker for osteoarthritis.