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

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

in the

anterior compartment of the leg The anterior compartment of the leg is a fascial compartment of the lower leg. It contains muscles that produce dorsiflexion and participate in inversion and eversion of the foot, as well as vascular and nervous elements, including the anterior ...

. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to 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 ...

Structure

The fibularis tertius arises from the lower third of the front surface 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 ...

, the lower part of the

interosseous membrane An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint. Interosseous membranes in the human body: * Interosseous membrane of forearm * Interosseous ...

, and

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interat ...

, or connective tissue, between it and 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 septum is sometimes called the intermuscular septum of Otto. The muscle passes downward and ends in a tendon that passes under the superior extensor retinaculum and the

inferior extensor retinaculum of the foot The inferior extensor retinaculum of the foot (cruciate crural ligament, lower part of anterior annular ligament) is a Y-shaped band placed in front of the ankle-joint, the stem of the Y being attached laterally to the upper surface of the calc ...

in the same canal as the

extensor digitorum longus muscle The extensor digitorum longus is a pennate muscle, situated at the lateral part of the front of the leg. Origin and insertion It arises from the lateral condyle of the tibia; from the upper three-quarters of the anterior surface of the body of ...

. It may be mistaken as a fifth tendon of the extensor digitorum longus. The tendon inserts into the medial part of the posterior surface of the shaft of the fifth

metatarsal bone 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 ...

. The fibularis tertius is supplied by the

deep fibular nerve The deep fibular nerve (also known as deep peroneal nerve) begins at the bifurcation of the common fibular nerve between the fibula and upper part of the fibularis longus, passes infero-medially, deep to the extensor digitorum longus, to the ante ...

. In rare cases, it may also be supplied by the common fibular nerve. This is unlike the other

fibularis muscles The fibularis muscles (also called peroneus muscles or peroneals) are a group of muscles in the lower leg. Description The muscle group is normally composed of three muscles: fibularis longus, fibularis brevis, and fibularis tertius. The fi ...

, which are located 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 ...

and are supplied by the

superficial fibular nerve The superficial fibular nerve (also known as superficial peroneal nerve) innervates the fibularis longus and fibularis brevis muscles and the skin over the antero-lateral aspect of the leg along with the greater part of the dorsum of the foot (wit ...

, since the fibularis tertius is found in the anterior compartment of the leg. The fibularis tertius may be absent in

humans" \n\n\n\n\nThe robots exclusion standard, also known as the robots exclusion protocol or simply robots.txt, is a standard used by websites to indicate to visiting web crawlers and other web robots which portions of the site they are allowed to visi ...

. It may be absent in as few as 5% of people, or as many as 72%, depending on the population surveyed. It is rarely found in other

primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter including ...

, which is one reason its function has been linked to efficient

bipedalism Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

Function

As a weak dorsiflexor of the ankle joint, the fibularis tertius assists in pulling the foot upward toward the body. It also assists in tilting the sole of the foot away from midline of the body at the ankle ( eversion). It is likely to be helpful though not essential in bipedal walking.

Clinical significance

The fibularis tertius may be involved in ankle injuries and may rupture. This is caused by

hyperextension 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 tertius may be imaged using

medical ultrasound Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, mu ...

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.

Other animals

The fibularis tertius muscle in

horses The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million ...

originates from the near the lateral condyle of the femur, passes through the extensor sulcus on the head 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 conn ...

, and inserts onto the third

, the third and fourth tarsal bones, and the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. ...

. Rupture of the muscle may cause the

Achilles tendon The Achilles tendon or heel cord, also known as the calcaneal tendon, is a tendon at the back of the lower leg, and is the thickest in the human body. It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcaneus ...

to have a slight dip.

Additional images

File:Peroneus tertius.png, Muscles of the front of the leg (fibularis tertius visible at center left). File:Gray268.png, Bones of the right foot (dorsal surface). File:Gray441.png, The mucous sheaths of the tendons around the ankle (lateral aspect). File:Slide1ABBAA.JPG, Dorsum of Foot. Deep dissection. File:Slide2ABBAA.JPG, Dorsum of Foot. Deep dissection.

References

External links

* - "The Leg: Muscles"
PTCentral
{{Authority control Muscles of the lower limb