Synovial Lipomatosis of the Knee: A Case Report and Review of the Literature.

Synovial lipomatosis (lipoma arborescens) is a rare, benign, intra-articular lesion characterized by villous proliferation of mature adipocytes, most commonly affecting the knee. Early recognition is essential to prevent misdiagnosis and long-term joint dysfunction. MRI is highly suggestive, while histopathology confirms the diagnosis. We describe the case of a 34-year-old male with persistent left knee monoarthritis. Laboratory investigations, including complete blood count, erythrocyte sedimentation rate, and C-reactive protein, were within normal limits. MRI showed frond-like synovial projections with fat-signal intensity suppressed on fat-saturated sequences. Histopathology confirmed the diagnosis of synovial lipomatosis. The patient underwent synovectomy, resulting in full resolution of symptoms and no recurrence during four months of follow-up. Synovial lipomatosis should be considered in patients with chronic knee effusion. MRI is usually diagnostic, and early arthroscopic synovectomy restores function, prevents degenerative changes, and achieves excellent outcomes.