Various etiologies have been proposed, including trauma, hemorrhage, chronic infection, and mucoid degeneration. The most widely accepted theory describes<unk> s resulting from extrusion of synovial fluid through a peripherally extended horizontal<unk>  tear, accumulating outside the joint capsule. They arise more commonly from the lateral joint margin, and occur most often in 20- to 40-year-old males.
Meniscal cyst
Osteochondroma
Retrocalcaneal bursitis
Osteochondrosis
Discoid meniscus
Olecranon bursitis
Synovial osteochondromatosis
Synovial chondromatosis