CASE REPORT Posterior tibial tendon impingement due to os subtibiale: a case report and up-to-date review Adil Turan 1 & Ozkan Kose 1,2 & Baver Acar 1 & Melih Unal 1 Received: 8 November 2016 /Revised: 6 February 2017 /Accepted: 8 February 2017 # ISS 2017 Abstract Os subtibiale is a rare accessory ossicle located at the tip of the medial malleolus. Although this small ossicle usually has no clinical significance, in some cases it may be a source of ankle pain. Symptomatic os subtibiale is an extreme- ly rare diagnosis, and few cases have been reported to date. The case presented is of a 35-year-old female patient with symptomatic os subtibiale, with a discussion of the diagnosis, clinical findings, and treatment options. Keywords Accessory ossicle . Os subtibiale . Medial malleolus . Symptomatic . Excision Introduction There are numerous accessory ossicles around the foot and ankle. Many of these are detected incidentally on plain radiographs taken for other reasons, and often have no clinical significance [1, 2]. Os subtibiale is a rare, rounded and well-corticated accessory ossicle lo- cated at the tip of the medial malleolus. The incidence of os subtibiale in radiographic survey studies has been reported to be between 0.2 and 1.2% [1–3]. Although os subtibiale is usually asymptomatic, it may cause impingement and irritation of the adjacent posterior tib- ial tendon (PTT), leading to a painful syndrome. This condition, in other words, symptomatic os subtibiale, is extremely rare and only a few cases have been reported in current English-language literature (Table 1)[4–9]. Owing to the apparent rarity, it was decided to report the following case of symptomatic os subtibiale in a young female patient. A review is also included of all previously published cases of symptomatic os subtibiale, and the imaging findings, clinical characteristics, and treatment options are discussed. Case report A 35-year-old woman presented at our clinic with pain in the posterior aspect of the medial malleolus, which had been ongoing for 3 months. The pain was dull and was exacerbated by walking and standing. On palpation, there was pain over the posterior edge of the medial malleolus and along the PTT. There were no other abnormal physical findings. Radiographs of the ankle showed a small ossicle located just inferior to the medial malleolus (Fig. 1). The patient reported no previous or recent ankle trauma. To exclude an avulsion fracture, com- puted tomography (CT) was applied to the ankle. CT imaging demonstrated that the ossicle was rounded and corticated and located just inferior to the posterior colliculus of the medial malleolus (Fig. 2). A volume rendered 3D CT image showed close contact between the ossicle and the PTT (Fig. 3). Further magnetic resonance (MR) imaging showed diffuse edema, particularly at the level of the medial malleolus and fluid within the PTT, suggesting tenosynovitis (Fig. 4). Based on the clinical and imaging findings, a diagnosis was made of * Ozkan Kose drozkankose@hotmail.com 1 Orthopedics and Traumatology Department, Antalya Training and Research Hospital, Antalya, Turkey 2 Kazım Karabekir cd. Antalya Eğitim ve Araştırma Hastanesi, 07100, Soğuksu Muratpaşa, Antalya, Turkey Skeletal Radiol DOI 10.1007/s00256-017-2601-1