Intraarticular benign tumors are rare lesions in many cases seen as incidental findings. One of the typical lesions is the diffuse or nodular form of pigmented villonodular synovitis, which needs a complete surgical removal. Magnetic Resonance Imaging (MRI) is diagnostic in most of the cases because of the intracellular iron content which shows an at least in some parts dark T2-sequence. Adjuvant therapies as radiosynoviorthesis should be considered in diffuse or recurrent lesions. Synovial Chondromatosis represents a metaplastic disorder of the synovial membrane resulting in the production of loose cartilage bodies. Also in this dissease synovectomy or, in late cases, removal of the loose bodies only, is recommended. Synovial hemangiomas are hamartomas which may lead to pain or restriction of movement. In these cases total or partial resection is justified. Alternative treatment options such as laserablation may be possible. Lipoma arborescens represents a proliferative lipoid lesion of the subsynovial region leading to villonodular synovial proliferation. If clinically symptomatic, resection by arthroscopic or open synovectomy is recommented.
Keywords: Bone tumors; Lipoma arborescens; Pigmented villonodular synovitis; Synovial chondromatosis; Synovial hemangioma.