Intra-articular Knee Lipomatous Tumor: Two Similar but Different Cases

Although lipomatous tumors are common, intra-articular occurrence is exceedingly rare and sparsely described in the literature. Regarding these rare entities, most are benign, progressively growing tumors and often occur in the knee, yet it is crucial to distinguish the less infrequent lipoma arborescens (LA) from the rarer synovial lipoma, as they differ in presentation and pathogenesis. Magnetic resonance imaging is the exam of choice in their assessment and in differential diagnosis, playing a central role nowadays. Excision and synovectomy, either arthroscopic or by arthrotomy, provide good outcomes with low recurrence rates. By reporting two surgically treated distinct cases of intra-articular lipomatous tumors of the knee, the authors intend to review the literature and discuss their etiology, clinical and imaging aspects as well as treatment approach.