Lipid composition of the tissues of human knee joints. II: Synovial fluid in trauma

Synovial fluid was aspirated from the knees of 125 patients and lipid profiles were determined. The patients had knee injuries with or without fracture of bone; these lipid profiles were compared with "controls" (synovial fluid obtained at surgery from patients that did not have a knee injury). Floating lipid droplets were observed in some of the synovial fluid from patients with fractures. These lipid droplets could be separated as a well-defined supernatant layer after a few minutes of centrifugation (100 X g). This layer was found to consist mostly of triglycerides. The synovial fluid from patients with fracture and those with only soft-tissue trauma showed increases in total lipids and triglyceride content but had lower phospholipids when compared with nontraumatized knees. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, cholesterol, monoglycerides, diglycerides, triglycerides, and free fatty acids were present in all synovial fluids assayed. The large amount of triglycerides in the synovial fluid in many cases may be a good indicator of marrow leakage. Because the soft tissue surrounding the knee is also rich in triglycerides, a low phospholipid level in some cases may be an even better indicator of marrow leakage.