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

lateral compartment of the leg The lateral compartment of the leg is a fascial compartment of the lower leg. It contains muscles which make eversion and plantarflexion of the foot. Muscles The lateral compartment of the leg contains: * Fibularis longus * Fibularis brevis ...

. 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 Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

) at the

ankle The ankle, or 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 joi ...

. 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 The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity i ...

, and its "belly" runs down along most of this bone. The muscle becomes a tendon that wraps around and behind the

lateral malleolus A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promine ...

of the

, then continues under the foot to attach to the

medial cuneiform There are three cuneiform ("wedge-shaped") bones in the human foot: * the first or medial cuneiform * the second or intermediate cuneiform, also known as the middle cuneiform * the third or lateral cuneiform They are located between the navic ...

and first

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

. 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 (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

. Between the muscle's attachments to the head and body of the fibula, there is a gap through which the

common fibular nerve The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...

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 In human anatomy, the fibularis brevis (or peroneus brevis) is a muscle that lies underneath the fibularis longus within 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 e ...

; 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 and then runs underneath the cuboid in a groove that is converted into a canal by the

long plantar ligament The long plantar ligament (long calcaneocuboid ligament; superficial long plantar ligament) is a long ligament on the underside of the foot that connects the calcaneus with the 2nd to 5th metatarsal. Structure The long plantar ligament is the l ...

. The tendon then crosses the sole of the foot at an angle and inserts into the lateral side of the base of the first

and the lateral side of the medial

cuneiform Cuneiform is a logo-syllabic script that was used to write several languages of the Ancient Middle East. The script was in active use from the early Bronze Age until the beginning of the Common Era. It is named for the characteristic wedge-sh ...

. Occasionally, it also sends a slip to the base of the second

. 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) 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 The tibialis posterior muscle is the most central of all the leg muscles, and is located in the deep posterior compartment of the leg. It is the key stabilizing muscle of the lower leg. Structure The tibialis posterior muscle originates on the ...

, extend the foot downward away from the body at the ankle (plantar flexion). It opposes the

tibialis anterior The tibialis anterior muscle is a muscle in humans that originates along the upper two-thirds of the lateral (outside) surface of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and inve ...

and the

fibularis tertius In human anatomy, the fibularis tertius (also known as the peroneus tertius) is a muscle in the anterior compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to pull the foot upward toward ...

, which pull the foot upward toward the body (

dorsiflexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

). 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 ''Terminologia Anatomica'' is the international standard for human anatomical terminology. It is developed by the Federative International Programme on Anatomical Terminology, a program of the International Federation of Associations of Anatomi ...

'' 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