The Fibularis Tertius is a small muscle located in the lower leg, specifically in the lateral compartment. It originates from the lower part of the fibula and inserts into the base of the fifth metatarsal bone in the foot. This muscle plays a role in dorsiflexion and eversion of the foot, helping to lift the foot and turn it outward. Although not present in everyone, the Fibularis Tertius is considered an accessory muscle to the more prominent fibularis longus and fibularis brevis. Its presence can vary among individuals, and it is often assessed during physical examinations for lower leg injuries or conditions.