Pain and swelling or focal mass at the level of the joint. The pain may be related to a<unk>  tear or distension of the knee capsule or both. The mass varies in consistency from soft/fluctuant to hard. Size is variable, and<unk> s are known to change in size with knee flexion/extension.
Meniscal cyst
Osteochondroma
Retrocalcaneal bursitis
Osteochondrosis
Discoid meniscus
Olecranon bursitis
Synovial osteochondromatosis
Synovial chondromatosis