(Kiosk 2) A Case of Newly Diagnosed Lipoma Arborescens

Case Diagnosis: Newly diagnosed lipoma arborescens in the right knee.

Case Description or Program Description: A 65-year-old male golf caddie with a past medical history of tricompartmental osteoarthritis presented to the outpatient clinic for a three-year history of chronic right knee pain located in the lateral joint line. He endorsed stabbing, sharp pain that is worse in the morning associated with persistent swelling. Previous X-ray imaging of the right knee indicated tricompartmental osteoarthritis, moderately severe in the lateral compartment. His osteoarthritis was conservatively managed with physical therapy, topical menthol, and NSAIDs, with minimal relief of symptoms. He was subsequently sent to complete an MRI of his right knee which revealed lipoma arborescens, degenerative maceration of his medial and lateral menisci, and synovitis.

Setting: Outpatient Clinic

Assessment/Results: The patient received a 3cc corticosteroid injection in the right knee using a landmark-guided anterolateral approach. Ultrasound was utilized prior to the injection to identify the optimal route of entry. Aspiration of the suprapatellar effusion was deferred as projections of the lipoma arborescens impeded entry. Two weeks after the intervention, the patient reported complete resolution of symptoms with increased range of motion of his right knee. The patient declined surgical evaluation due to work schedule.

Discussion (relevance): Lipoma arborescens is a rare, benign intra-articular lesion characterized by villous proliferation of the synovium and diffuse replacement of the subsynovial tissue by mature fat cells. This condition is typically monoarticular and should be considered in the differential diagnosis of a slowly progressive chronically swollen knee. Although complete excision is typically considered the standard treatment, this case highlights the importance of considering more conservative measures like corticosteroid injections.

Conclusions: This case demonstrates the efficacy of conservative measures like corticosteroid injections for the rare condition of lipoma arborescens. This case also highlights the importance of utilizing ultrasound-guided interventions for patients with complex anatomy.