Why Do Clinicians Inject Fat Into The Joint Space?
Adipose tissue is made of collagen that does not degrade in the presence of synovial fluid or plasminogen and has cells embedded within its matrix.
Inside the joint, bleeding occurs after injury, but no fibrin-platelet plug is observed to form.(1) Circulating intra-articular plasmin breaks down the fibrin plug as fast as it can form. (1,3,4) While human Platelets release a fast-acting plasmin inhibitor, the high levels of plasminogen in the synovium overwhelms the natural process of the platelet fibrin clot. (2) Thus healing of tissue inside a joint has proved difficult.(1) Tissue outside the joint such as the medial collateral ligament is typically not exposed to synovial fluid after injury and is not as challenging a tissue to heal. (1) While the cellular composition of the two ligaments are similar, their microenvironments are different. (1) Scaffolds that are not made out of fibrin, such as Collagen, the primary structure of fat, does not degrade in the presence of plasminogen. (1,5) The ideal biologic tissue inside the joint should contain platelets to prevent premature degradation, collagen from fat or other source, growth factors, and stem cells to begin the tissue regeneration process.
1. Martha M. Murray et al Collagen-Platelet Rich Plasma Hydrogel Enhances Primary Repair of the Porcine Anterior Cruciate Ligament J Orthop Res 25:81–91, 2007
2. Hansen et al Partial Purification and Characterization of a New Fast-Acting Plasmin Inhibitor from Human Platelets EVIDENCE FOR NON-IDENTITY WITH THE KNOWN PLASMA PROTEINASE INHIBITORS Biochem. J. (1980) 187, 173-180 7,173-180 173 Printed in Great Britain
3. Rosc D, et al Post-traumatic plasminogenesis in intraarticular exudate in the knee joint. Med. Sci. Monit.2002;8:371–378. [PubMed]
4. Carmassi F, et al Elastase- and plasmin-mediated fibrinolysis in rheumatoid arthritis. Int. J. Tissue React. 1994;16:89–93. [PubMed]
5. Smith SA, et al Polyphosphate enhances fibrin clot structure. Blood.2008;112:2810–2816.