Fig. 4

Pathologic appearance of the excised semimembranosus-medial collateral ligament bursal body. The intraoperative ex situ gross appearance of the bursa demonstrated multiple fragments of firm, white, nodular and fatty soft tissue. On cut sections, the fragments were either pale, white, and firm or lobulated and yellow (A). Histologically, the tissue was composed primarily of coalescing nodules of mature hyaline cartilage surrounding foci of mineralization (B: hematoxylin and eosin stain, 40× magnification). Higher magnification showing mature chondrocytes chondrocytes within lacunae (arrowheads) surrounded by cartilaginous matrix (blue-green) (C: Alcian blue stain, 200× magnification). The chondroid matrix multifocally surrounded regions of dystrophic mineralization (brown staining; arrows) (D: Von Kossa stain, 100× magnification). The remaining surface synovium consisted of mildly hypertrophied synoviocytes and lymphoplasmacytic inflammation (asterisks) in concert with reactive neovascularization (arrows) (E: hematoxylin and eosin stain, 200× magnification). Mature fibrillar collagen (blue), often in association with small blood vessels, was observed at the periphery of the cartilaginous nodules (asterisk) (F: Masson’s trichrome stain, 40× magnification)