Flexor hallucis brevis muscle 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 ...

of the

foot The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg mad ...

that flexes the

big toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plan ...

Structure

Flexor hallucis brevis muscle arises, by a pointed tendinous process, from the medial part of the under surface of the cuboid bone, from the contiguous portion of the third

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- ...

, and from the prolongation of the tendon of the

tibialis posterior muscle 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 th ...

which is attached to that bone. It divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly ...

of the great toe, a

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

bone being present in each tendon at its insertion. The medial portion is blended with the

abductor hallucis muscle The abductor hallucis muscle is an intrinsic muscle of the foot. It participates in the abduction and flexion of the great toe. Structure The abductor hallucis muscle is located in the medial border of the foot and contributes to form the promin ...

previous to its insertion; the lateral portion (sometimes described as the first plantar interosseus) with the

adductor hallucis muscle The Adductor hallucis (Adductor obliquus hallucis) arises by two heads—oblique and transverse and is responsible for adducting the big toe. It has two heads, both are innervated by the lateral plantar nerve. Structure Oblique head The ''oblique ...

. The tendon of the

flexor hallucis longus muscle The flexor hallucis longus muscle (FHL) is one of the three deep muscles of the posterior compartment of the leg that attaches to the plantar surface of the distal phalanx of the great toe. The other deep muscles are the flexor digitorum longus an ...

lies in a groove between the two. Its tendon usually contains two sesamoid bones at the point under the first

metatarsophalangeal joint The metatarsophalangeal joints (MTP joints), also informally known as toe knuckles, are the joints between the metatarsal bones of the foot and the proximal bones ( proximal phalanges) of the toes. They are condyloid joints, meaning that an elli ...

Innervation

The medial and lateral head of the flexor hallucis brevis is innervated by the

medial plantar nerve The medial plantar nerve (internal plantar nerve) is the larger of the two terminal divisions of the tibial nerve (medial and lateral plantar nerve), which accompanies the medial plantar artery. From its origin under the laciniate ligament it pa ...

. Both heads are represented by spinal segments S1, S2.

Variation

Origin subject to considerable variation; it often receives fibers from 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. ...

or long plantar ligament. Attachment to the cuboid bone sometimes wanting. Slip to first phalanx of the second toe.

Function

Flexor hallucis brevis flexes the first

metatarsophalangeal The metatarsophalangeal joints (MTP joints), also informally known as toe knuckles, are the joints between the metatarsal bones of the foot and the proximal bones (proximal phalanges) of the toes. They are condyloid joints, meaning that an ellipti ...

joint, or the

. It helps to maintain the medial longitudinal arch. It assists with the toe-off phase of gait providing increased push-off.

Clinical significance

Sesamoid bones contained within the tendon of flexor hallucis brevis muscle may become damaged during

exercise Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...

Additional images

Image:Gray269.png, Bones of the right foot. Plantar surface. File:Slide1ABA.JPG, Flexor hallucis brevis muscle File:Slide8ABA.JPG, Flexor hallucis brevis muscle

References

External links

PTCentral
{{Authority control Foot muscles Muscles of the lower limb