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.