Quadratus plantae muscle
Quadratus plantae, also called the flexor accessorius is one of the central plantar muscles of the foot. Observing the foot muscles horizontally, quadratus plantae comprises the second layer of plantar foot muscles, together with the lumbricals.
The function of this muscle is to facilitate walking by shortening the flexor digitorum longus' tendons when the foot is in plantar flexion. Hence its other name; flexor accessorius.
This article will discuss anatomy and function of the quadratus plantae muscle.
|Origin||Medial surface of calcaneus bone, lateral process of calcaneal tuberosity|
|Insertion||Tendon of flexor digitorum longus|
|Action||Metatarsophalangeal joints 2-5: Toe flexion|
|Innervation||Lateral plantar nerve (S1-S3)|
|Blood supply||Medial plantar artery, lateral plantar artery, deep plantar arterial arch|
Origin and insertion
Quadratus plantae is a two-headed muscle, consisting of medial and lateral heads. The heads are separated by the long plantar ligament and they originate from different sites on the calcaneus.
The medial head originates from the medial surface of calcaneus, just inferiorly to the calcaneal groove for flexor hallucis longus muscle. The lateral head is smaller and tendinous, and it originates from the lateral process of calcaneal tuberosity. Both heads insert onto the tendon of flexor digitorum longus, at the point where it splits into its four terminal tendons. This particular site of insertion enables the quadratus plantae to incorporate its tendinous slips into all four digital tendons of flexor digitorum longus and thus influence the flexion of the toes. However, some variations may be seen; when the lateral two digital tendons of flexor digitorum longus do not receive the slips from quadratus plantae.
The muscle is situated deep to the flexor digitorum brevis and superficial to the adductor hallucis muscle. Lateral plantar artery and nerve course over its superficial surface, while medial plantar artery and nerve pass medially to the muscle.
This muscle is supplied by the lateral plantar nerve (S1, S3), which stems from the tibial nerve.
Blood supply to this muscle comes from branches of posterior tibial artery;
- Medial plantar artery
- Lateral plantar artery and its branch; deep plantar arterial arch
When it contracts, this muscle pulls the tendons of the flexor digitorum longus towards the calcaneus. This is especially significant in transition from stance to swing phase of gait, when the foot is in plantar flexion. In that position, flexor digitorum is already shortened and cannot flex the toes to grip. However, quadratus plantae assists by shortening the long flexor tendons even more, flexing the toes and enabling the foot propulsion off the ground.
Need help in understanding the function of the foot muscles? Check out our learning materials about the foot muscles.
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