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Peroneus Longus


- Anatomy:
    - lateral compartment
    - plantar muscles of the foot:
    - origin:
         - lateral condyle of tibia, head and proximal 2/3 of lateral surface of fibula, intermuscular septa and adjacent fascia;
    - course:
         - peroneus longus courses posteiror to the brevis tendon, and then both tendons pass thru the common peroneal synovial sheath, 
                about 4 cm proximal to the lateral malleolus;
         - synovial sheath passess through a fibro-osseous tunnel that is stabilized by the superior peroneal retinaculum and by the calcaneofibular 
         - after the peroneus longus emerges from its sheath and passes inferior to the cuboid on its way to its insertion;
         - os peroneum is an accessory bone which is located within the peroneus longus tendon in about 20% of feet;
                - typically this is located plantar to the cuboid, near the calcaneo-cuboid articulation;
                - this accessory ossicle may be associated with peroneus longus tenosynovitis;
    - insertion:
         - lateral margin of plantar surface of 1st cuniform and proximal end of 1st metatarsal.
    - action:
         - primary action is to plantar flex the first ray of the foot;
         - plantar flexion and eversion of the foot at the ankle;
         - primarily active during the stance phase of gait;
         - gives lateral stability to the ankle;
         - synergists: gastrocnemius, soleus;
    - nerve supply:
         - peroneal, S1 > L5, L4; (see innervation)

Pathologic Conditions:
    - peroneal tendon subluxation:
    - peroneal tendon disruption:
         - persistent swelling along the peroneal tendon sheath is a reliable sign for peroneus brevis tendon tear;
    - peroneal muscle spasm:
         - may occur w/ tarsal coalition, but may also occur w/ rheumatoid arthritis, osteochondral frx, & infection in subtalar joint or 
                neoplasm (osteoid osteoma, fibrosarc)
    - Charcot Marie Tooth:
         - when there is loss of the tibialis anterior and peroneus brevis (which is common in CMT), the peroneus longus will cause flexion 
                of the first ray, which subsequently leads to a cavus foot deformity;
    - polio:
         - in polio syndrome, transfer of the peroneus longus in the presence of strong tibialis anterior results in a dorsal bunion as the 
                forefoot supinates;
         - it must be combined with lateral transfer of the tibialis anterior to the base of the second metatarsal bone

Peroneal tendon injuries.