Objective: To quantify inflammatory changes in synovial membranes from orthopedic "non-inflammatory" arthropathies (Orth.A).
Methods: Synovial membranes (n=23; femur fracture, avascular necrosis of the femur, plica syndrome, and meniscus and/or ligament injury), RA [n=28], OA [n=25], and normal controls [n=10]) were assessed by light microscopy, a histologic synovitis score, immunostaining for CD3, CD20, CD38, CD68, Ki-67 and von Willebrand Factor, and with an immunohistochemical inflammation score.
Results: Orth.A histology varied between normal and markedly inflamed. Predominant abnormalities were mild lining hyperplasia, scattered inflammatory cells, and small perivascular infiltrates. The synovitis score classified Orth.A as "mild synovitis". Inflammatory cells occurred frequently: CD68+ cells in 100% of Orth.A specimens; CD3+, 91%; CD38+, 70%; and CD20+, 39%. Orth.A had greater lining thickness (p=0.04), vascular density (p=0.009) and CD38+ cell density (p=0.02) than normal controls, and fewer subintimal Ki-67+ cells (p=0.003) and lining and subintimal CD68+ cells (p<0.01) than OA. The immunohistochemical inflammation score was 2.2-fold higher in Orth.A than in controls (p=0.048) and similar to OA, with 3 Orth.A specimens showing marked inflammation.
Conclusions: Synovial membranes from "non-inflammatory" arthropathies featured neovascularization and inflammation intermediate between normal and OA synovium. These results expand previous findings that mechanical joint injury may lead to a mild-to-moderate synovitis.
- Plica syndrome
- avascular necrosis
- meniscus injury