Which feature describes OA pathology in the synovium?

• A. Proliferation of synoviocytes and macrophages leading to hyperplasia of the synovial lining
• B. MMP production and cytokine release leading to pyroptosis and necrosis
• C. New blood vessel formation leading to worsening inflammation
• D. Decreased synovial fluid production

Answer: (A)

OA affects the joint with a low-grade, chronic synovitis where the lining of the synovium becomes noticeably thickened as synoviocytes and macrophages proliferate. This hyperplasia of the synovial lining reflects ongoing local inflammatory activity and is a classic feature seen in OA joints. The proliferating synoviocytes and infiltrating macrophages release inflammatory mediators and matrix metalloproteinases that contribute to cartilage breakdown and perpetuate joint damage.

While cytokines and MMPs are involved in OA, the idea of inflammatory cell death such as pyroptosis and necrosis isn’t a typical hallmark of OA synovitis. Angiogenesis can be seen in synovitis generally, but it isn’t the defining feature of OA synovial pathology. Decreased production of synovial fluid isn’t characteristic either; OA can have effusions, but the key synovial change is the hyperplastic lining from cellular proliferation.