Radiological Case: Bilateral Synchronous Involvement of Knee and Hip Joints With Primary Lipoma Arborescence in a Young Male

Ashwini Bakde Umredkar, MD; Amit Disawal, MD; Aarti Anand, MD; Prajwalit Gaur, MD; Jasdeep Kaur, MBBS


Appl Radiol. 2017;46(10):24-28. 

In This Article

Imaging Findings

The patient was referred to the radiology department for bilateral knee joint and hip radiography. Radiography of both knee joints AP and lateral view (Figure 1B and 1C) revealed soft tissue swelling in the suprapatellar region. There were no bone erosions.

Radiography of both hip joints with pelvis (Figure 1D) revealed displacement of fat stripes along the left hip joint, s/o possibly left hip joint effusion. Visualized bones were normal.

Patient was then referred for further evaluation by ultrasound of both knees and MRI of both the knees and hips for further evaluation.

Ultrasound of the knee (Figure 2A and 2B) was performed by high frequency linear probe, which revealed bilateral knee joint effusion with collection in the suprapatellar region. There was frond-like hyper echoic synovial growth, which was seen projecting into the collection.

Figure 2.

Ultrasound of the suprapatellar region on right (A) and left sides (B) showing frond-like hyper echoic synovial growth which is seen projecting into the large fluid collection in the suprapatellar region.

MRI of the knee and hip joints was performed using dedicated knee coil on 1.5 Tesla Philips MR Achieva, which revealed frond-like villous proliferation of the synovium in bilateral knee joint and suprapatellar compartment, which showed fatty signal on T1W (Figure 3A) and T2W image (Figure 3B). There was complete loss of fatty signal from the villous projections on fat suppressed STIR images (Figure 3C and 3D). There was associated large collection in bilateral suprapatellar compartment with mild collection in bilateral patello-femoral and tibio-femoral compartment.

Figure 3.

MRI knee axial image T1W Sequence (A) showing hyperintense frond-like fatty synovial proliferation. Sagittal image of the knee T2W Sequence (B) showing fatty synovial proliferation with knee joint effusion. Sagittal image of the knee STIR sequence (C) showing complete suppression of fat signal from the frond-like growth which is appearing hypointense. Coronal Image of both knee joints STIR sequence (D) showing bilateral suprapatellar effusion with frond-like hypointense synovial growth.

A diagnosis of lipoma arborescence of bilateral knee joint and suprapatellar compartment was made based on classical imaging findings of fat signal intensity frond-like synovial proliferation with associated effusion.

MRI of both hip joints revealed similar lipomatous synovial proliferation with mild joint effusion on both sides (Figure 4A and 4B).

Figure 4.

MRI both HIP joints, T2W Coronal images (A) showing frond-like fatty synovial proliferation which appears hyper intense on T2W. Both hip joints STIR images (B) show complete signal loss from synovial growth. Bilateral mild hip joint effusion is noted. Also noted gross effusion in bilateral suprapatellar pouch.

Patient underwent excision of the lipomatous growth with synovectomy of the right knee followed by left with relief of his symptoms. Specimen was sent for histopathological examination, which revealed villous projections lined by synovial epithelium with sub epithelial tissue comprised of predominantly fat, intervening blood vessels and chronic inflammatory infiltrate of histiocytes, plasma cells and lymphocytes. Gross pathological and histopathological findings were consistent with diagnosis of lipoma arborescence (Figure 5A and 5B).

Figure 5.

Gross specimen (A) showing greyish white tissue with multiple polypoidal projections studded over its external surface. Photomicrograph of the histopathological specimen (B) showing multiple villous projections lined by synovial epithelium with sub epithelial fat cells, intervening blood cells and chronic inflammatory infiltrate.