Journal of Postgraduate Medicine
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Year : 1995  |  Volume : 41  |  Issue : 4  |  Page : 113-4  

Solitary synovial osteochondroma of the knee.

VN Allahabadia, SS Kulkarni, AS Dogra, PB Bhosale 
 Dept of Orthopaedics, Seth GS Medical College, Parel, Bombay.

Correspondence Address:
V N Allahabadia
Dept of Orthopaedics, Seth GS Medical College, Parel, Bombay.


A very rare case of solitary osteochondroma of the knee is reported. The patient presented with a slowly growing retropatellar bony tumour of 4 years duration following a minor trauma. An excisional biopsy with a total patellectomy was performed as the patellar articular surface was unsalvageable. A 20 month follow up revealed no recurrence and a functional knee. A brief review of literature is also presented.

How to cite this article:
Allahabadia V N, Kulkarni S S, Dogra A S, Bhosale P B. Solitary synovial osteochondroma of the knee. J Postgrad Med 1995;41:113-4

How to cite this URL:
Allahabadia V N, Kulkarni S S, Dogra A S, Bhosale P B. Solitary synovial osteochondroma of the knee. J Postgrad Med [serial online] 1995 [cited 2022 Jul 2 ];41:113-4
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  ::   IntroductionTop

Synovial chondromatosis has been discussed widely in literature[1]. However solitary osteochondroma is an extremely uncommon entity and few reports are available in literature. This rare tumour is usually seen in the hands and feet. We present here an interesting case where it was found in the knee joint.

  ::   Case reportTop

A 32 year old housewife, sustained a minor trauma to her left knee region 4 years ago which was treated by massage. She complained of a progressively increasing swelling with restriction of her range of motion over the 4 year period. There was no other significant contributory history. On examination there was a diffuse, solitary, bony hard swelling, anteromedial to the left patella, extending to the retro patellar region, with normal overlying skin. The range of movements at the left knee was 30? to 90?, and no patella femoral movement was detectable. There was minimal tenderness over the tibial tuberosity. There was no ligamentous laxity or distal neurovascular deficit. The swelling was not palpable in the popliteal fossa. There was quadriceps wasting and no palpable inguinal lymph nodes. All other joints were normal. Roentgenograms of the left knee, AP, lateral and skyline views [Figure:1], showed a solitary, calcified, intra-articular, irregular, retro patellar mass with erosion of the articular surface of the patella.

99m Technetium bone scan revealed localised increased uptake. Rest of the scan was normal. Serum calcium was  9.5 mg % (Normal 911 mg %) Serum inorganic phosphorus  4 mg % (Normal 34.5 mg %) Serum alkaline phosphatase  10 KA units (Normal 313 KA units) Rest of the biochemical investigations were unremarkable.

As the history, clinical findings and investigations were suggestive of a benign tumour, it was decided to perform an excisional biopsy through an anteromedial para patellar incision. On exploration, a solitary, gritty, bony hard tumour, 4 x 3 x 6 cms was found arising from the synovium and eroding the posterior and inferior surface of the patella. There was also some extension into the anterior cruciate ligament and the posterior aspect of the patellar tendon. The tumour along With its overlying folds of synovium was excised. Since the patellar articular surface was beyond salvage, a total patellectomy was performed, Intra and postoperative period was uneventful, the limb being immobilised in a cylinder cast for a period of 6 weeks. Gradual mobilisation was then started. Histopathologically, the tumour was proved to be an osteochondroma.

At a 20 month followup, the range of movement at the left knee was 0 to 100?, without any pain. There was no evidence of local recurrence. The patient could perform all daily activities without discomfort [Figure:2]

  ::   DiscussionTop

Solitary synovial osteochondroma is a rare variant of synovial osteochondromatosis. These tumours arise from the synovial cells themselves or the primitive cells lying within the synovium[1]. These tumours are formed probably by metaplasia of the synovial cells to chondrocytes, giving rise to islands of cartilage within the synovium, which then lead to multiple loose bodies within the joint cavity with secondary mineralization[2]. Solitary synovial osteochondroma is not connected to bone and occurs almost exclusively in the vicinity of the joints in hands and feet. There has been a single case report of a solitary synovial osteochondroma around the knee[3]. Other rare presentations include a carpal tunnel syndrome[4]. A review of literature failed to disclose a case with malignant transformation although local recurrence has been reported, in some, more than once[2], and hence a subtotal synovectomy has been advised. In our case, there has been no recurrence in a period of 20 months and the functional result is good following the local excision of the tumour.


1 Fechner RE. Neoplasms and Neoplasmlike Lesions of the Synovium; in Tones and Joints", edited by Ackermann LLV, Spjut HJ, Abell MR, Williams and Wilkins Co., Baltimore: 1976; 1571M
2Minsinger WE, Balogh K, Millender LH. Tenosynovial Osteochondroma of the hand. A case report and brief review. Clin Orthop 1985; 196:24852.
3Shih WJ, Ryo UY. Synovial osteochondroma of the knee it Tc 99m HMDP Bone Imaging. Clin Nucl Med 1988; 13 (8):617-18.
4Nather AA, Chong PY. A rare case of carpal tunnel syndrome due to tenosynovial osteochondroma. J Hand Surg (Br) 1986; 11 (3): 47880.

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