Lipoma Arborescens: a cause of chronic synovitis?

Lipoma arborescens is an uncommon cause of intra-articular masses that presents as slowly progressive painless swelling of the joint, which persists for many years and is accompanied by intermittent effusions. Extra-articular site(s) involvement is unusual, but can occur in tendon sheaths and bursas. Magnetic resonance imaging is the best diagnostic exam, although synovial biopsy may be necessary. We report three cases in order to highlight the clinical spectrum and imaging features of the disease, so that early diagnosis and appropriate treatment can be given. (author)