Serum keratan sulfate levels in osteoarthritis patients.

Serum levels of keratan sulfate (KS), measured by an enzyme-linked immunosorbent-inhibition assay, were found to be significantly higher in 31 patients with hypertrophic osteoarthritis (OA) than those in 41 adults without joint disease. Seventy-seven percent of patients with OA, but only 12% of control subjects, had serum levels which were more than 1 SD above the mean of the control group. Following replacement of a single osteoarthritic hip joint, serum KS levels decreased, at first, in all patients. Subsequently, the concentration of serum KS progressively increased; 6 months following surgery, KS levels were similar or close to the preoperative levels in virtually all patients. The results suggest that patients with hypertrophic OA may have a generalized imbalance of cartilage proteoglycan metabolism. Measurements of serum KS are likely to prove most useful in studying this particular subset of patients with generalized OA.