A 16-year-old professional female ballet student sustained a plantar flexion-inversion injury to her left ankle while dancing. Clinical examination and MRI suggested subluxation of the tibiotalar joint. However, accurate diagnosis was hampered by a transient palsy of the common peroneal nerve. It was subsequently established that she had also sustained a dislocation of her calcaneocuboid joint, a rare injury, which was successfully stabilised by using a hamstring graft. The presentation and management of this rare condition are discussed.

We have assessed the proximal capsular extension of the ankle joint in 18 patients who had a contrast-enhanced MRI ankle arthrogram in order to delineate the capsular attachments.

We noted consistent proximal capsular extensions anterior to the distal tibia and in the tibiofibular recess. The mean capsular extension anterior to the distal tibia was 9.6 mm (4.9 to 27.0) proximal to the anteroinferior tibial margin and 3.8 mm (−2.1 to 9.3) proximal to the dome of the tibial plafond. In the tibiofibular recess, the mean capsular extension was 19.2 mm (12.7 to 38.0) proximal to the anteroinferior tibial margin and 13.4 mm (5.8 to 20.5) proximal to the dome of the tibial plafond.

These areas of proximal capsular extensions run the risk of being traversed during the insertion of finewires for the treatment of fractures of the distal tibia. Surgeons using these techniques should be aware of this anatomy in order to minimise the risk of septic arthritis.