Extra-articular osteochondromatosis: A collection of four clinical cases of different localization

Synovial chondromatosis is known to be frequently intra-articular and more rarely extra-articular. We present four cases of extra-articular chondromatosis in four different localizations: in the retro-olecranon bursa, in the sheath of the flexor of hallucis longus muscle, in the extra-synovial space of the knee and within the muscle’s fibers of brachialis muscle. Plain radiography, ultrasonography, tomodensitometry and magnetic resonance imaging show imaging characteristics, which help in differential diagnosis. Surgical excision is the gold standard treatment to avoid recurrence or malignancy transformation and to achieve a normal articular mobility.