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76 m a s s a g e & b o d y wo r k n ove m b e r/d e ce m b e r 2 0 2 2 Fibularis Longus By Christy Cael The fibularis longus is a muscle located along the full length of the lateral leg. It is contained within the lateral compartment along with the fibularis brevis muscle. The muscle belly is relatively superficial and originates on the head and proximal portion of the lateral fibula. Moving distally, its tendon runs behind the lateral malleolus, extends from lateral to medial across the bottom of the foot, and inserts near the anterior tibialis on the medial side. Together, the fibularis longus and anterior tibialis muscles form a structure called the anatomical stirrup, describing the way the two muscles sling around the bottom of the foot. This structure helps support medial arch and control movement of the foot from side to side. The location of the fibularis longus allows it to contribute to ankle plantar f lexion, as well as strongly perform ankle eversion. The fibularis brevis is a synergist in both motions, where the fibularis tertius is synergistic in ankle eversion alone. The tertius is positioned more anteriorly, giving it leverage for ankle dorsif lexion rather than plantar f lexion like the longus and brevis. Ankle eversion helps position the foot before planting it on the ground during gait and is also used when moving the body from side to side. The fibularis longus, along with the other fibularis muscles, helps pull the center of gravity from medial to lateral over the planted foot. This side-stepping movement is common when walking over and around objects. Ankle eversion also helps initiate and control direction changes. Activities that require pushing with the legs 76 m a s s a g e & b o d y wo r k n ove m b e r/d e ce m b e r 2 0 2 2 essential skills | FUNCTIONAL ANATOMY SPINALIS Attachments • Origin: Head and lateral two-thirds of the fibula • Insertion: Lateral sides of the first metatarsal and medial cuneiform Actions • Plantar flexes the ankle • Everts the foot Innervation • Superficial fibular nerve • L5-S1 Fibularis longus