CASE REPORT Instability of the proximal tibiofibular joint, an unusual cause for knee pain Ulfin Rethnam * , A. Sinha Glan Clwyd Hospital, North Wales, UK Accepted 2 November 2005 Introduction Knee pain is not an uncommon presentation in the A&E. We present a case report of an unusual cause for knee pain–—instability of the proximal tibiofibu- lar joint. Case report A 45-year-old male presented with left knee pain and instability while running after sustaining a kick to the knee. The pain was anterior, constant in nature and radiated to the thigh and leg. It was aggravated by running and came on if he sat for long periods. On examination there was no effusion and no specific local tenderness. He had a full range of pain-free movement of the knee. There was no valgus or varus instability and Lachman’s and poster- ior draw tests were negative. There was no clinical evidence of meniscal pathology or common pero- neal nerve palsy. Radiographs of the knee were unremarkable. Initial management with analgesics and phy- siotherapy brought no relief, so an isotope bone scan was performed. This showed an increased uptake in the region of the head of the left fibula (Fig. 1). Magnetic resonance imaging of the left knee revealed a fluid collection at the proximal tibiofibular joint (Figs. 2 and 3). The proximal tibiofibular joint was then injected with local anaesthetic, which relieved the pain. The fibular head was partially resected, which gave complete relief. At one year he remained symp- tom free, except for occasional anterolateral leg pain. Discussion Chronic instability of the proximal tibiofibular joint is an uncommon diagnosis and is not fre- quently reported in the literature. 5 Instability at this joint may be anterolateral, posteromedial, superior 2 or inferior. 1 Patients usually present with lateral knee pain and instability with popping or catching, which may be confused with a lateral meniscal injury. 2 Axial CT scanning, which is the investigation of choice, 1 can make the diagnosis. The treatment options for chronic pain or instabil- ity and secondary arthritis include arthrodesis of the proximal tibiofibular joint, fibular head resec- tion, proximal tibiofibular joint capsular and liga- ment reconstruction with the biceps femoris tendon 3 or an autogenous biceps tendon graft tenodesis. 4 Injury Extra (2006) 37, 190—192 www.elsevier.com/locate/inext * Corresponding author at: 18 Bron Y Nant, Croesnewydd Road, Wrexham LL13 7TX, UK. Tel.: +44 7779095559. E-mail address: ulfinr@yahoo.com (U. Rethnam). 1572-3461/$ — see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2005.11.004