Synovial fluid lipids in normal individuals and patients with rheumatoid arthritis

Normal human synovial fluid contains trace amounts of phospholipids and cholesterol. Phospholipid composition is similar to that in serum. Rheumatoid synovial fluid contains increased amounts of phospholipid, cholesterol, and neutral lipids. In most cases the concentration is 40 to 60 per cent of that found in simultaneously collected serum specimens. A direct relationship appears to exist between total synovial fluid protein and lipid concentration. No relationship could be established between lipid content in rheumatoid synovial fluid, and total cell content, hyaluronic acid, severity or duration of synovitis in the involved joint.