This case shows a split tear of the peroneus brevis tendon as well as intra-sheath subluxation of the peroneal tendons (type B) 1.
Dynamic ultrasound is necessary to diagnose intra-sheath subluxation which involves the peroneal tendons switching positions during specific movements of the ankle. Static imaging may result in a false negative result.
The patient is positioned prone on the examination table with the foot projecting beyond the table to allow dorsiflexion and eversion of the ankle. The transducer is oriented in the axial plane.
Case submitted by Mathew Illimoottil in collaboration with Shashank Gupta (medical student at Loyola University).