Villous lipomatous proliferation of the synovial membrane (lipoma arborescens).

The cases of five patients (7 knees) who had villous lipomatous proliferation of the synovial tissue (lipoma arborescens) are reported. The longest duration of symptoms was thirty years. Six of the seven knees were treated by synovectomy. The length of follow-up ranged from two to eleven years, and six knees were followed for five years or more. The patients who were treated by synovectomy had complete healing of the synovial lesion, but the osteoarthritis tended to progress, especially in patients who had long-standing symptoms. Because of the clinical, macroscopic, and microscopic features of this rare disease, we suggest discarding the name lipoma arborescens, which implies that the lesion is a neoplasm, and using the more descriptive term of villous lipomatous proliferation of the synovial membrane.