Giant Cell Tumour of the Tendon Sheath – an Unusual Cause for Locking of the Knee Joint

Letters Giant cell tumour of the tendon sheath-an unusual cause for lockinG of the knee joint. Editor, Locking of the knee is a common presentation at orthopaedic outpatient departments. These patients normally require magnetic resonance imaging (MRI) where there is a clinical suspicion of a soft tissue lesion. The most common lesions are meniscal tears and typically present with associated pain. We present an unusual case of a giant cell tumour arising from the tendon sheath causing painless locking of the knee joint. case report: A 39-year-old male presented with a twelve-month history of painless locking in his left knee. He worked as a roofer and found his symptoms worse when climbing ladders. He was referred by his general practitioner who suspected a meniscal tear. There was no history of any trauma to the knee. Clinical examination revealed no swelling, effusion or joint line tenderness around the knee, and a full range of movement. A mass arising from the medial aspect of his patella, which was mobile within the knee joint, was palpable. The lesion was firm but not bony in nature, and was not visible on X-ray. The mass was presumed to be a soft tissue lesion and, because of the hazards associated with his occupation, the patient proceeded directly to arthroscopy rather than MRI. At arthroscopy a large intra-articular lesion was identified originating posterior to the medial patella. The size of the lesion prohibited removal during arthroscopy, and was therefore excised in its entirety via a medial parapatellar incision. Histology showed the specimen to be a giant cell tumour of the tendon sheath measuring 40 x 35 x 15mm (Fig 1). Postoperative recovery was uneventful and at two-month review the patients symptoms had resolved. discussion: Giant cell tumours of the tendon sheath (GCTTS) are benign soft tissue masses, typically found on the flexor surface of the hand and wrist 1. They are more common in males with an average age of presentation of 30-50 years 2. These tumours are classified in two types; the common localized type and the rare diffuse type. The more localised form accounts for 88% of cases effecting the hands and feet arising from the synovium of the tendon sheath 2. It is unusual for giant cell tumours to involve larger joints and to be intra-articular. In large joints diagnosis is difficult because the signs and symptoms can be non-specific 3. The rare diffuse …