In human anatomy, the fibularis longus (also known as peroneus longus) is a superficial

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

in the lateral compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to extend the foot downward away from the body ( plantar flexion) at the

ankle The ankle, the talocrural region or the jumping bone (informal) is the area where the foot and the leg meet. The ankle includes three joints: the ankle joint proper or talocrural joint, the subtalar joint, and the inferior tibiofibular joint. The ...

. The fibularis longus is the longest and most superficial of the three fibularis (peroneus) muscles. At its upper end, it is attached to the head of the fibula, and its "belly" runs down along most of this bone. The muscle becomes a tendon that wraps around and behind the lateral malleolus of the

, then continues under the foot to attach to the medial cuneiform and first metatarsal. It is supplied by the superficial fibular nerve.

Structure

The fibularis longus arises from the head and upper two-thirds of the lateral, or outward, surface of the fibula, from the deep surface of the fascia, and from the connective tissue between it and the muscles on the front and back of the leg. It occasionally is also connected by a few fibers from the lateral condyle of the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

. Between the muscle's attachments to the head and body of the fibula, there is a gap through which the common fibular nerve passes to the front of the leg.'' Gray's Anatomy (1918), see infobox'' The muscle ends in a long tendon, which runs behind the lateral malleolus of the ankle in a groove that it shares with the tendon of the fibularis brevis; the groove is converted into a canal by the superior fibular retinaculum, and the tendons in it are contained in a common mucous sheath. The tendon then extends forward at an angle across the lateral side of the foot, below the fibular trochlea and the tendon of the fibularis brevis, and under cover of the inferior fibular retinaculum. It crosses the lateral side of the

cuboid In geometry, a cuboid is a hexahedron with quadrilateral faces, meaning it is a polyhedron with six Face (geometry), faces; it has eight Vertex (geometry), vertices and twelve Edge (geometry), edges. A ''rectangular cuboid'' (sometimes also calle ...

and then runs underneath the cuboid in a groove that is converted into a canal by the long plantar ligament. The tendon then crosses the sole of the foot at an angle and inserts into the lateral side of the base of the first metatarsal and the lateral side of the medial

cuneiform Cuneiform is a Logogram, logo-Syllabary, syllabic writing system that was used to write several languages of the Ancient Near East. The script was in active use from the early Bronze Age until the beginning of the Common Era. Cuneiform script ...

. Occasionally, it also sends a slip to the base of the second metatarsal. The tendon changes direction at two points: first, behind the lateral malleolus; second, on the cuboid bone. In both of these locations, the tendon is thickened. At the cuboid, a fibrocartilaginous sesamoid (sometimes a

sesamoid bone In anatomy, a sesamoid bone () is a bone embedded within a tendon or a muscle. Its name is derived from the Greek word for 'sesame seed', indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be presen ...

) usually develops in the substance of the tendon. The fibularis longus muscle is supplied by the superficial fibular nerve, which arises from the fifth lumbar and first sacral roots of the spinal cord.

Function

The fibularis longus, together with the fibularis brevis and the tibialis posterior, extend the foot downward away from the body at the ankle (plantar flexion). It opposes the tibialis anterior and the fibularis tertius, which pull the foot upward toward the body ( dorsiflexion). The fibularis longus also tilts the sole of the foot away from the midline of the body ( eversion). Because of the angle at which it crosses the sole of the foot, it plays an important role in maintaining the transverse arch of the foot. Together, the fibularis muscles help to steady the leg upon the foot, especially in standing on one leg.

Nomenclature and etymology

'' Terminologia Anatomica'' designates "fibularis" as the preferred word over "peroneus.". The word "peroneus" comes from the Greek word "perone," meaning pin of a brooch or a buckle. In medical terminology, the word refers to being of or relating to the fibula or to the outer portion of the leg.

Additional images

References

{{Authority control Muscles of the lower limb

Structure

Function

Nomenclature and etymology

Additional images

See also

References