Dr. Ebraheim’s educational animated video describes the anatomy of the Peroneus Brevis muscle.
The peroneus brevis muscle passes down the outside of the lower leg and lies under the peroneus longus. The peroneus brevis is shorter and has a smaller muscle belly compared to the peroneus longus.
Peroneus brevis muscle is located within the lateral compartment of the lower leg. The lateral compartment of the lower leg contains both the peroneus longus and the peroneus brevis muscles. The lateral compartment also contains the superficial peroneal nerve. Both muscles of the lateral compartment are innervated by the superficial peroneal nerve.
The peroneal artery supplies blood to both of the peroneal muscles in the lateral compartment of the leg. Both the peroneus brevis and the peroneus longus muscles originate from the fibular shaft. The origin of the peroneus brevis comes from the inferior 2/3 of the lateral aspect of the shaft of the fibula. The peroneus brevis is then inserted into the lateral aspect of the base of the 5th metatarsal bone. The peroneus brevis becomes tendinous approximately 2-4 cm proximal to the tip of the lateral malleolus. The origin of the peroneus longus muscle comes from the head of the fibula and the upper 2/3 of the lateral aspect of the fibula. It also originates from the anterior and posterior intermuscular septa of the leg. The peroneus longus tendon is inserted into the plantar posterolateral aspect of the medial cuneiform and lateral side of 1st metatarsal base.
The peroneal tendons are contained in a common synovial sheath. Both tendons curve around the tip of the fibula anteriorly with the peroneal tubercle separating the tendons at the level of the calcaneus. At the level of the tubercle, the peroneus brevis is dorsal and the peroneus longus is plantar.
After the level of the calcaneus, the peroneus longus tendon curves sharply, making a 90 degree turn medially and passing in a groove beneath the cuboid where it crosses to the plantar aspect of the foot before inserting medially into the base of the 1st metatarsal and the medial cunifrom.
There are two peroneal retinacula which hold the two peroneal tendons at the ankle (superior and inferior). The superior peroneal retinacula is more important than the inferior retinaculum. The superior retinaculum is located in the distal 3 cm of the fibula. The superior retinaculum originates form the posterolateral ridge of the fibula and inserts into the lateral calcaneous (prevents subluxation). The inferior retinaculum is continuous with the inferior extensor retinaculum. Behind the fibula, the tendons run in a sulcus called the peroneal groove which is found on the fibula posteriorly. The tendons are stabilized by the superior peroneal retnaculum and the cartilaginous rim. Within the groove, the peroneus brevis tendon is anterior and medial to the peroneus longus. Both tendons curve anteriorly around the tip of the fibula.
The peroneus brevis tendon may sublux or dislocate due to superior peroneal retinaculum rupture or avulsion. A longitudinal tear of the peroneus brevis tendon may also occur. The tear of the peroneus brevis occurs because the tendon of the peroneus brevis is closer to the fibula than the tendon of the peroneus longus. The superficial peroneal nerve supplies the peroneal muscles (L5,S1,S2).
The peroneus brevis muscle everts the hindfoot. Both peroneal muscles plantar flex the ankle. The primary function of the peroneus longus is to plantar flex the first ray of the foot.
Two important variations have been implicated in association with tendon tears, pathology and instability. The peroneus quartus is present in about 20% of the patients and may crowd tunnel for the superior retinaculum. A low lying peroneus brevis muscle belly may also be implicated in tendon instability, tendonitis or tears.
Important considerations
•The peroneus brevis muscle is the main everter of the hindfoot and is an antagonist to the tibialis posterior muscle.
•Longitudinal split of the peroneus brevis tendon can occur with peroneal tendon subluxation.
•Avulsion of the base of th fifth metatarsal can occur due to pull of the peroneus brevis muscle.
•The belly of the peroneus brevis muscle is much lower then the muscle belly of the peroneus longus.
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Background music provided as a free download from YouTube Audio Library.
Song Title: Every Step
