Macroscopic and microscopic features of synovial membrane inflammation in the osteoarthritic knee: Correlating magnetic resonance imaging findings with disease severity

Abstract

Objective. To determine the magnetic resonance imaging (MRI), macroscopic, and microscopic characteristics of synovial membrane inflammation, to study the relationship between disease severity and the degree of synovial inflammation on MRI and on macroscopic and microscopic examination, and to look for colocalization of chondral lesions and synovial inflammation.Methods. Thirty-nine patients with knee osteoarthritis (OA) were classified into 2 groups according to the severity of cartilage lesions as revealed by chondroscopy. Group 1 (n ‫؍‬ 14) had mild cartilage lesion(s) without exposure of subchondral bone. Group 2 (n ‫؍‬ 25) had severe cartilage lesion(s) with focal or diffuse exposure of subchondral bone. Synovitis was evaluated on T1-weighted MRI sequences according to the degree of synovial thickening on a 4-point scale (ranging from 0 to 3) in 5 regions of interest. Synovial membrane was macroscopically scored, and biopsies were performed on the 5 preselected sites for histologic scoring.Results. The mean ؎ SD synovial thickening score on MRI was 1.55 ؎ 0.90, with no significant difference between groups 1 and 2. Intra-and interobserver reproducibility of the total synovial score was excellent, and interobserver reproducibility of the MRI grade was good. Conclusion. Synovitis may be present from the onset of OA and may be evaluated on MRI. MRI evaluation of synovitis could be used to classify OA patients in clinical trials and could help to identify those who could benefit from synovium-targeted therapy.Osteoarthritis (OA) is the most prevalent form of arthritis and a major cause of disability worldwide (1).

The role of synovitis in osteoarthritis

“…Biopsies from the synovium of OA knees (taken at arthroscopy for knee pain or at joint replacement) have demonstrated several key changes in the synovium, which although more pronounced in advanced OA, are present from the earliest stages of the OA process [Loeuille et al 2005;Smith et al 1997;Myers et al 1990]. These synovial abnormalities include: thickening of the lining layer; increased vascularity; inflammatory cell infiltration.…”

The peroxisome proliferator–activated receptor γ agonist pioglitazone reduces the development of cartilage lesions in an experimental dog model of osteoarthritis: In vivo protective effects mediated through the inhibition of key signaling and catabolic pathways

“…Lesional joint cartilage in the placebo-treated group exhibited morphologic changes, including cartilage fibrillation and fissures, changes in cellularity, such as cloning and hypocellularity, and loss of Safranin O staining, as previously described (11,20,21) (Figure 2). A decrease in the histologic score of the medial femoral condyles, indicative of a reduced severity of the lesions, was observed in dogs with OA treated with pioglitazone (median histologic score 6.25 [range [3][4][5][6][7][8][9][10][11][12] in the placebo group versus 4.25 [range [3][4][5][6][7] in the 15 mg/day pioglitazone group and 5.5 [range [5][6] in the 30 mg/day pioglitazone group); this difference was sig- nificant following a dosage of 15 mg/day pioglitazone as compared with the placebo group (P Ͻ 0.05). This reduction in histologic scores was mainly related to a protective effect of pioglitazone treatment on the severity of structural changes and the loss of Safranin O staining.…”

“…Synovial inflammation, a common finding in patients with symptomatic OA, has also been demonstrated to contribute to the evolution of structural changes in the disease (9,10). This latter phenomenon is probably related to the synthesis and release, by the synovial membrane, of factors that are capable of inducing cartilage catabolism and other structural changes (1).…”

B Cell Clonal Expansion and Somatic Hypermutation of Ig Variable Heavy Chain Genes in the Synovial Membrane of Patients with Osteoarthritis

“…O steoarthritis (OA) 3 is generally considered as a noninflammatory disease, but some degree of inflammation is often found in symptomatic OA cases (1)(2)(3). At macroscopic inspection, half of the patients with knee OA depict synovial abnormalities, which were shown to be associated with more severe chondropathy (4).…”