The synovial fluid is a thick gel-like liquid that helps cushion the knee and acts to absorb the daily impact of walking and running and stair climbing our knees are subjected to. The synovial membrane lines the joint capsule and helps maintain synovial fluid in joints. Inflammation of the synovial membrane, synovitis, is found in both rheumatoid and osteoarthritis patients. Doctors use synovial fluid as a means to understand inflammation in the knee.
Doctors at the University of Calgary, publishing in the medical journal Osteoarthritis and Cartilage, suggest that knee joint instability leads to destructive alterations in the synovial membranes and cartilage. Their research conclusion was that knee joint instability may promote an inflammatory intraarticular milieu (a diseased joint environment), thereby contributing to the development of osteoarthritis.1
New research is out testing the theory that synovial inflammation of the knee is a main and unrecognized player is the development of knee osteoarthritis.
Doctors in Taiwan publishing in the medical journal Experimental gerontology examined the effects of Platelet Rich Plasma on synovial fluid volumes, protein concentrations, and severity of pain in patients with knee osteoarthritis. Here is their research summary:
- Patients with knee osteoarthritis are often complicated with joint soreness, swelling, weakness, and pain. These complaints are often caused by the excessive amount of synovial fluid accumulated in the bursae around the knee joint.
- They examined the effectiveness of platelet rich plasma in treating patients with minor to moderate knee osteoarthritis combined with supra-patellar bursitis.
- Twenty-four elderly patients with minor to moderate knee osteoarthritis combined with supra-patellar bursitis were recruited.
- Aspiration of the synovial fluid was performed under ultrasound followed by subsequent PRP injections.
- Three monthly PRP injections were performed to the affected knees for a total of 3 months.
- Approximately after the 2nd PRP injection, significant decreases in synovial fluid total protein concentrations and volumes (signifying a decrease in inflammation), and Lequesne index values (this is a value given to measure the severity of knee osteoarthritis) were observed.
- Therefore, at least two monthly PRP injections may be beneficial for treating patients with minor to moderate knee osteoarthritis combined with supra-patellar bursitis.2
Doctors at the University of Toronto tested the effects of stem cell in early and late-stage knee osteoarthritis by measuring the stem cell cytokine secretion (small proteins which initiate healing and rebuilding of damaged tissue) after it was exposed to arthritic synovial fluid obtained from early- vs late-stage knee osteoarthritis patients.
Following exposure to the osteoarthritic synovial fluid and a three day culture period, the stem cells secreted proteins involved in tissue repair, angiogenesis (development of new blood vessels), chemotaxis (migration of cells to the injured tissue), matrix remodeling (wound healing) and the clotting process. However, chemokine (white blood cell response to injury or infection) ligand-8 (influences cell migration to site of infection or injury), interleukin-6 (a pro- and anti-inflammatory) and chemokine (influences cell migration to site of infection or injury) were elevated in the earlier stages of knee osteoarthritis. Signalling that early vs late stage osteoarthritis patients need to be treated differently when employing stem cells.3
1 Chen CPC, Cheng CH, Hsu CC, Lin HC, Tsai YR, Chen JL. The influence of platelet rich plasma on synovial fluid volumes, protein concentrations, and severity of pain in patients with knee osteoarthritis. Exp Gerontol. 2017 Apr 20;93:68-72. [Pubmed]
2 Gómez-Aristizábal A, Sharma A, Bakooshli MA, Kapoor M, Gilbert PM, Viswanathan S, Gandhi R. Stage-specific differences in secretory profile of mesenchymal stromal cells (MSCs) subjected to early- vs late-stage OA synovial fluid. Osteoarthritis Cartilage. 2017 May;25(5):737-741. [Pubmed]
3 Egloff C, Hart DA, Hewitt C, Vavken P, Valderrabano V, Herzog W.Joint instability leads to long-term alterations to knee synovium and osteoarthritis in a rabbit model. Osteoarthritis Cartilage. 2016 Jun;24(6):1054-60. [Pubmed]