Case Report

Primary Lipoma Arborescence of Bilateral Knees in an Adolescent Patient: A Case Report

by Alexander Speechley1*, Matthew J Brown2

1School of Medicine University of St. Andrews, N Haugh, St Andrews KY16 9TF, UK

2Connecticut Children’s Sports Medicine, 399 Farmington Ave., Farmington, CT, 06032. United States

*Corresponding author: Alexander Speechley, School of Medicine University of St. Andrews, N Haugh, St Andrews KY16 9TF, UK and Matthew J Brown, Connecticut Children’s Sports Medicine, 399 Farmington Ave., Farmington, CT, 06032, United States

Received Date: 11 January 2024

Accepted Date: 16 January 2024

Published Date: 19 January 2024

Citation: Speechley A, Brown MJ (2024) Primary Lipoma Arborescence of Bilateral Knees in an Adolescent Patient: A Case Report. Ann Case Report 09: 1596.


Introduction: Lipoma Arborescens is benign lesion presenting with deposits of adipose tissue forming villous, frond-like synovial growths, with the knee most commonly affected. Case: An adolescent male presented with bilateral knee pain and was found to possess lipoma arborescens in both knees. He underwent bilateral arthroscopic synovectomy after the failure of nonoperative modalities. Synovectomy was successful, and the patient was able to return to full activities after three months of physical therapy. Conclusion: This case study investigates the rare case of a pediatric bilateral lipoma arborescens patient treated successfully with arthroscopic synovectomy, and the usage a GraftNet device in obtaining tissue for histological analysis.


Lipoma Arborescens (LA) is a rare, synovial proliferation characterized by a dense, villous appearance involving the synovial joints [1]. A handful of cases can be seen throughout medical literature, but since its discovery in the early 20th century, LA remains poorly understood. The term originates from "arbor" meaning "tree" in latin illustrating the gross and “frond-like” appearance that the synovial mass commonly presents [2]. The suprapatellar recess of the knee is the most frequent location but the shoulder is also an occasional site [3-5]. In the majority of cases, synovectomy is the recommended treatment for improvement in pain and function. Rarely, non-operative means can manage symptoms. Along with advanced imaging, characterization via pathology is important to most accurately determine morphology.

We present a brief case of bilateral LA in a 15- year-old male and the role of the GraftNetTM Autologous Tissue Collector (Arthrex, Naples, FL) in capturing adequate pathological sampling for this uncommon tumor-like lesion.

Case Report

A 14-year-old male presented to pediatric orthopedic clinic complaining of bilateral knee pain for several years. He had seen another partner in the office for this concern and had completed more than 20 sessions of physical therapy over the previous few months with no significant relief. He endorsed pain on the right greater than the left and stated the pain had been going on for approximately seven years and noticed it most with activities such as squatting and running. The patient was simultaneously being worked on by another pediatric specialist for problems with chronic constipation as well as bilateral testalgia of unknown cause.

Initial knee exam revealed palpable grinding in flexion and extension along with mechanical symptoms associated with meniscal provocative maneuvers. Initial plain films of both knees showed slight lateral patellar tilt but no other evidence of abnormality such as fractures or dislocations.  On physical examination there were palpable protuberant masses in the bilateral suprapatellar pouches with baseline knee effusions. Investigation with bilateral knee MRIs was pursued.

MRI of bilateral knees demonstrated synovitis along with diffuse lipomatous disease consistent with LA (Figure 1).  After a thorough review of the MRI findings with the patient and his mother concerning surgical versus nonsurgical options, a decision was made to trial physical therapy for an additional 6 weeks before considering surgery.  On follow-up, the patient continued to report worsening bilateral knee pain despite continued physical therapy. After repeat discussion about surgical options the decision was made to pursue exploratory arthroscopy as well as synovectomy of the right knee first, per patient request (Figure 2).


Figure 1: Sagittal T2 MRI demonstrating lipoma arborescens in the suprapatellar pouch.


Figure 2: Lipoma arborescens seen in suprapatellar pouch during arthroscopy.

That month, the patient underwent a right knee synovectomy due to worsening pain secondary to LA. After a diagnostic arthroscopy was performed on each knee, the patellofemoral compartment was investigated for articular injury. Upon exploration, there was immediate visualization of lipomatous fronds in the supra-patellar pouch. The medial and lateral compartments were pristine without injury or evidence of loose bodies. The supra-patellar pouch was debrided using a combination of the two existing antero-medial and antero-lateral portals along with the lateral supra-patellar portal. Utilizing the GraftNet device, we sent two separate samples to pathology from the supra-patellar region in addition to samples obtained using a biter. Due to the extensiveness of the diseased synovium, we then made a postero-medial portal under scope guidance and then debrided the villous lipomas in the back of the knee. All wounds were then copiously irrigated with saline, and the incisions were closed. The samples of the synovial villiform projections taken using both the GraftNet device and a manual biter and sent to pathology for histological examination (Figure 3) were consistent with LA.