Torsion of an intra-articular lipoma as a cause of pseudo locking of the knee

Knee Locking in Osteoarthritis due to Synovial Lipoma: A Case Report

“…Rarely, it may present with sudden pain which is caused by the torsion of the stalk of lipoma, if it is pedunculated [6,7]. In the present case, patient presented with pain and episodic locking of the left knee joint.…”

“…Lipoma arborescens is grossly characterized by numerous villous projections of fatty synovial tissue within the joint and microscopically by patchy lipomatous metaplasia which is intermixed with a proliferating synovium [2]. The true Intraarticular lipoma clinically presents with a variable symptomatology and it is microscopically characterized by well defined lobules of fatty tissue which are lined by a hyperplastic, synovial epithelium [2,6,7]. Lipoma arborescens is usually associated with post-traumatic or inflammatory joint conditions, but it also may arise de novo.…”

“…Rarely, it may transform to a liposarcoma [6,7]. Considering the magnitude of above complications, a Synovial lipoma requires immediate excision.…”

Orthopaedic Case of the Month: A Painless Right Knee Mass in a 55-year-old Woman

“…Intraarticular lipomas usually present with a painless enlarged knee mass, locked knee, joint swelling, or a painful knee caused by strangulation of the intraarticular lipoma [10,27,28]. A true intraarticular lipoma typically is a solitary yellowish, variable-sized, solitary polyp-like mass, round to oval, with a short stalk connecting the joint capsule grossly.…”

“…Intraarticular lipomas with osteochondroid metaplasia or osseous metaplasia have been reported and have a possible association with repeated trauma [17,24]. Therefore, an intraarticular lipoma is a true neoplastic tumor of unknown etiology [24,28]. The indolent slow-growing clinical courses of an intraarticular lipoma without metastasis similar to a subcutaneous lipoma were observed clinically.…”