Peroneal tendon dislocation
This patient presented to the orthopedic surgeon 6 weeks after trauma to the left ankle, where the ankle briefly had become stuck between two cars. He complained of pain and weakness on the lateral side of the foot.
Initial radiographs showed an oblong ossification in soft tissue swelling lateral of the lateral malleolus. MRI several months later showed a lateral dislocation of the peroneal tendons and a markedly flat peroneal groove (a configuration thought to predispose to luxation).
Finally a bone scan with a SPECT-CT visualized both feet, showing persistent asymmetry in the peroneal tendon courses, flat peroneal concavities bilaterally and no increased bone turnover that might explain the symptoms.
This case is somewhat unusual in that there is a persistent, chronic luxation of the peroneus brevis tendon. After failure of the superior peroneal retinaculum, recurrent (sub)luxations can also been seen, typically on ultrasound. The markedly flat peroneal grooves this patient possesses might play a role in his pathology.