Hypertrophied Synovium

Plain radiographs can be normal or show intra-articular effusion, an ill-defined para-articular soft-tissue mass and, in longstanding disease, juxta-articular bone erosions and subchondral cysts caused by pressure and hypertrophied synovium. CT shows hemosiderin and fat deposits, and is able to detect bone erosions that are not manifest on radiographs. 

Apart from intermetatarsal bursitis, superficial palpable bursitis can occur in the midfoot over a hypertrophied peroneal tubercle and in the forefoot involving the adventitial bursae beneath the metatarsal heads (Ashman et al. 2001). A distended bursa underlying the head of the first metatarsal is often observed in association with hallux valgus (Schweitzer et al. 1999). It can be recognized as a focal mass with mixed echotexture (containing fluid and hypertrophied synovium) interrupting the subcutaneous fat plane focally (Fig. 17.57). 

Rheumatoid arthritis (RA) is an inflammatory disease of the synovium which results in erosion, deformity and finally the destruction of joints. Inflammation of the joints is associated with a villous hypertrophy of the synovial membrane, which on microscopy shows proliferation of the lining layer with an inflammatory infiltrate. There is extensive expression of HLA-... 

In rheumatoid arthritis, chronic synovitis leads to hypertrophy and hyperplasia of the synovium (pannus), progressive thinning of the articular cartilage and exposure of the subchondral bone. In early disease, when the cartilage still retains a certain thickness, the pannus typically causes marginal bone erosions, located at the periphery of the joint. 

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