There are two muscles in the lateral compartment of the leg:

• Fibularis longus

• Fibularis brevis.

Both muscles help evert the foot, meaning they are controlled by the superficial fibular nerve.

Both the fibularis longus and brevis muscles evert the foot (turn the sole outward) and aid in plantarflexion (point the toes downward). 

The longus also supports the arches of the foot. Both are innervated by the superficial fibular nerve, making them key muscles for balance and stability, especially on uneven surfaces.

Fibularis Longus

The fibularis longus is the larger and more superficial of the two muscles. It turns the sole of the foot outward (eversion) and points the toes downward (plantarflexion). It also helps support the arches of the foot. 

Its fibers form a tendon that runs down the leg behind the lateral malleolus (the outer ankle bone). The tendon passes under the foot to attach to the medial cuneiform and the base of the first metatarsal (near the big toe).

• Origin: Upper and outer surface of the fibula.

• Innervation: Superficial fibular (peroneal) nerve.

Fibularis Brevis

The fibularis brevis lies underneath the fibularis longus and is shorter in length. It helps evert the foot and assists in plantarflexion.

Its tendon travels down the leg, passing behind the lateral malleolus and over the calcaneus (heel bone) and cuboid bones. It attaches to a small bump on the base of the fifth metatarsal (on the outer side of the foot).

• Origin: Lower two-thirds of the outer surface of the fibula.

• Innervation: Superficial fibular (peroneal) nerve.

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