Relation between Synovitis and Knee osteoarthritis
Osteoarthritis (OA) is the most common cause of musculoskeletal pain and disability in the knee joint. OA starts as the lack or loss of this articulate (surface) cartilage and then progresses into involvement with the surrounding bone, tissues, and synovial fluid. In OA, cartilage may have areas of partial thinning or complete loss of surface cartilage resulting in areas of exposed bone. Symptoms of OA include joint pain with activity, night pain, morning stiffness, limited motion, joint inflammation, crepitus or noise from the knee, and deformity.
Synovitis is the inflammation of synovial membranes. It may occur in association with arthritis as well as lupus, gout. Previously, synovitis in OA was believed to be a consequence of underlying joint damage, with synovial inflammation resulting from macrophage phagocytosis of intra-articular cartilage or bone debris, calcium pyrophosphate dihydrate or calcium hydroxyapatite crystals with release of soluble cartilage matrix macromolecules. To identify the independent relation of synovitis with incident radiographic knee OA after adjusting for other structural factors known to cause synovitis, a study was conducted.
MRIs from knees were examined that were developed by incident radiographic OA from the Multicenter Osteoarthritis Study (MOST) and were compared with controls that did not develop OA. Base line MRIs for knees developing OA at any time up to 84 months of follow up. Lesions observed in cartilage, meniscus, bone marrow and synovitis were scored. Synovitis scores were summed (0-9) across three regions, suprapatellar, infrapatellar and intercondylar region, each of which was scored 0-3. After bivariate analyses examining each factor's association with incidence, multivariable regression analyses adjusted for age, sex, BMI, alignment and cartilage and meniscal damage were carried out.
After the analysis, 239 cases and 731 control knees were studied. In bivariate analyses, cartilage lesions, meniscal damage and bone marrow lesions were all risk factors for OA. After multivariable analyses, synovitis associated with incident OA, risk of a higher synovitis was increased with OA, but increased risk was associated only with synovitis scores of ≥3. Results indicated that synovitis, especially when there was a substantial volume within the knee has been proven to be an independent cause of OA.