Intra-articular lipoma arborescens of the knee joint

Lipoma arborescens - Uncommon Diagnosis for Joint Swelling: Case Report and Review of the Literature

INTRODUCTION

Soft tissue swelling of the knee joint can be caused by many diseases. Lipomas are one of the most reasonable differential diagnoses we have to consider. Therefore, we now present the uncommon case of a Lipoma arborescens (LA) and differentiate it from a quite similar manifesting spindle cell lipoma as follows.

CASE REPORT

A 49-years old patient reports about progressive knee pain for four years and observes an increasing joint swelling. This swelling is a soft tissue, shiftable tumour, not painful. The magnetic resonance imaging (MRI) with contrast agent brings the diagnosis of an advanced osteoarthritis of the knee joint and classifies the tumour as LA. Subsequently, we treat the osteoarthritis by implanting a total knee arthroplasty with simultaneous intraoperative tumour resection performed as total synovectomy. The histopathological processing confirms the clinically and radiologically made diagnosis of LA.

SUMMARY

Lipoma arborescens presents an uncommon subgroup of Lipomas, which is characterized by a slowly progressive increasing soft tissue swelling, especially around bigger human joints. Due to its intraarticular location, the LA might become clinically relevant when it reaches a certain tumour size. Looking at the diagnostics, sonography, MRI and especially the histopathological processing give the crucial results. Final proof can only be made by histopathological examination. Additionally, we have some differential diagnoses to exclude. Under these we predominantly find the spindle cell lipoma, synovial haemagioma, vascular synovial malformations and tenosynovial giant-cell tumour. Furthermore, an atypical lipomatous tumour should be excluded by FISH-analysis via determining the MDM2-Genamplification.

Synovial lipomatosis: A rare cause of knee pain in an adolescent female

Synovial lipomatosis is a benign proliferative disease of the subsynovial adipose which can lead to a variety of presentations. Cases of synovial lipomatosis in children or adolescents are rare. This case report describes an adolescent patient with a rare bilateral presentation of synovial lipomatosis. She had been treated for years prior to her presentation for juvenile idiopathic arthritis. She presented with chronic bilateral knee pain, swelling, and mechanical symptoms. Bilateral MR imaging demonstrated effusions, hypertrophy of the synovium, and polyp-like projections of tissue with the same signal intensity as fat which is pathognomonic for synovial lipomatosis. Arthroscopic synovectomy and extensive debridement of polyp like fat projections of the right knee was performed. Histopathology was consistent with the synovial lipomatosis diagnosis. Postoperatively, the patient was satisfied with her outcome with improved pain relief and function in her right knee.