R Chopra, CU Dussa, G Morgan, N Al-Mokhtar
Mr R Chopra, Trust Doctor Trauma & Orthopaedics, Princess of Wales hospital, Bridgend, UK, CF31 1RQ. Email: rajatchopra@hotmail.com
Mr Chakravarthy U Dussa, Research Fellow, Department of Orthopaedics, Princess of Wales hospital, Bridgend, UK, CF 31 1RQ. Email; dussacu1@msn.com
Mr G Morgan, Consultant Orthopaedics, Princess of Wales hospital, Bridgend, UK, CF 31 1RQ. Email: gerallt.morgan@bromor-tr.wales.nhs.uk
N.Al- Mokhtar, Consultant Radiology, Princess of Wales hospital, Bridgend, UK, CF 31 1RQ. Email: namir.al-mokhtar@bromor-tr.wales.nhs.uk
Address for correspondence: Mr R Chopra, MMBS, MRCS (Glasgow), 16 Underwood Road, Handsworthwood, Birmingham.B20 1JH
E-mail; choprarajat@hotmail.com
Abstract
Lipoma arborescens
is an uncommon pseudo tumoral synovial lesion commonly affecting the knee joint.
We report a case of Lipoma arborescens with an unusual presentation mimicking
leaky popliteal artery aneurysm.
Introduction
Lipoma arborescens is an uncommon pseudo tumoral synovial lesion. It commonly presents as painless, recurrent swelling of anterior compartment of knee joint. (1-8) We report a case of unusual presentation of lipoma arborescens, which presented clinically with a pulsatile swelling in the back of the knee and haemarthrosis, mimicking leaky aneurysm of popliteal artery.
Case report
A 61-year-old gentleman presented to Accident and Emergency department with a painful swelling in his left knee. He gave a history of a sudden onset of knee swelling that started 5 weeks prior to his presentation to the hospital. There was no history of trauma. He gave a past history of knee swelling following a trivial trauma 3 years ago. He attended accident and emergency and his knee aspirate showed 150 ml of blood. He was treated in RJ bandage. Following this he remained asymptomatic for 3 years until the current episode. He gives past history of Gout, and Osteoarthritis of knees.
General examination was normal. Physical examination of knee showed a large, tense suprapatellar swelling reaching proximally to upper third of thigh. The swelling was warm and non-tender. Patellar Tap was present. There was no distal neurovascular deficit. Examination of the Popliteal fossa showed a pulsatile swelling, situated in the centre of popliteal fossa. On palpation, expansile pulsations were noted. These pulsations correlated with the prominent left Popliteal artery pulsations. Under aseptic precautions, using a 20 ml syringe knee was aspirated. Around 360 ml of fresh blood was aspirated. Examination of knee after aspiration showed, decrease in size of pulsatile swelling in popliteal fossa.
Clotting profile, full blood count and inflammatory markers were within normal limits. Radiographs of left knee showed tricompartmental Osteoarthrosis (Figure 1 & 2). Ultrasound scan of knee was done. It showed posterior displacement of popliteal artery and vein by low-level echogenic structure, which was probably related to joint. No popliteal aneurysm demonstrated (Figure 3). Ultrasound of suprapatellar pouch demonstrated vascular ‘Frond-like’ like echogenic structure (Figure 4). However no specific diagnosis could be made. MRI scan was done .it demonstrated a large ‘Frond like’ synovial growth, mainly in the anterior compartment of the joint. This was associated with large joint effusion. Very little enhancement was seen following contrast and the lesion characteristics were consistent with lipoma arborescens (Figure 5 & 6). No hemosiderin pigment was demonstrated. Patient was managed conservatively on regular follow up. However patient was informed that if he remains symptomatic then he might require Arthroscopic synovectomy.
Discussion
Arzimanoglu in 1957 first described lipoma arborescens. (1). It is a benign lesion. Lipoma arborescens is characterised by diffuse replacement of the subsynovial tissue by mature fat cells, producing prominent villous transformation of the synovium. The term “Villous Lipomatous proliferation of the synovium” is some times used to differentiate Lipoma arborescens from synovial Lipoma and Hoffa’s disease. Because of the extensive or diffuse synovial proliferation of fatty tissue that characterizes this disorder (4, 6, 8, 10, 14)
The commonest joint involved is the knee joint. However, occasionally wrist, hip and ankle may be involved (4, 6). The aetiology of this condition is unknown (14). The origin of Lipoma arborescens is hypothesised to be either traumatic or inflammatory. It is frequently associated with osteoarthritis in younger patients and diabetes mellitus. It usually present with recurrent suprapatellar knee effusion. Associated popliteal cysts are noted in 20% of cases. (4, 7, 8, 10, 14)
Differential diagnosis in our patient could be pigmented villo-nodular synovitis. Both can present with knee swelling associated haemarthrosis. However, the characteristic features of Lipoma arborescens on MRI can make this distinction.
MRI outlines the synovial mass and readily reveals its frond like appearance. On T1-weighted images, it shows a high signal intensity frond like growth. However, on fat suppression sequences they became dark indicating high fatty contents. The absence of ferrous-pigmented granules, which are dark in all the sequences, distinguishes it from pigmented villo-nodular synovitis (5, 11, 13, 14). Literature recommends either arthroscopic or open synovectomy as treatment. Though majority of the cases in the literature had open synovectomy, arthroscopic synovectomy was found to be equally effective. However these were only sporadic reports (2, 3, 4, 5, 8, 10, 12). Anecdotal use of chemical cauterisation with Osmic acid has also been mentioned with good short-term success (9). We treated our patient was treated conservatively as the frequency of his symptoms are infrequent.
The unusual features in our patient are: our patient is older in contrast to the usual presentation in younger age group. He had no clear history of either trauma or diabetes mellitus. Though he presented with a Suprapatellar knee swelling, the pulsatile swelling in the popliteal fossa misled us to the possibility of a leaking aneurysm into the knee joint. Aspiration of fresh blood from the knee added to the diagnostic dilemma. Though US scan excluded the presence of an aneurysm, the appearance on MRI was pathgnomonic. Absence of clinical suspicion and awareness of this condition, as a cause of recurrent haemarthrosis in the knee delays its diagnosis.
.
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