Fig. 3

Schematic diagrams of the normal anatomy around the proximal end of the peroneus longus and peroneal nerve (a). Lateral compartment syndrome may result from a peroneus longus tear leading to peroneal nerve palsy (b). The common peroneal nerve (CPN) pierces the deep fascia and lies over the fibular neck, which forms the floor of the short ‘fibular tunnel’ (FT), and passes the lateral compartment just behind the peroneus longus. Idiopathic deep peroneal nerve entrapment can occur at the level of the fibular tunnel behind the peroneus longus, because hematoma beside the fibular tunnel increases lateral compartment pressure. CPN common peroneal nerve, S superficial peroneal nerve, D deep peroneal nerve, BF biceps femoris muscle, AF apex of the fibula, FT fibular tunnel, AIS anterior intermuscular septum, PL peroneus longus, GC gastrocnemius. The oval filled by oblique lines represents hematoma