Quadratus Plantae Muscle – Anatomy, Nerve Supply, Function

Quadratus Plantae Muscle is a muscle in the sole of the foot, typically originating from the calcaneus and inserting into the posterolateral surface of the tendons of flexor digitorum longus. It is implicated in heel pain, claw toe deformity and diabetic polyneuropathy. Phylogenetic considerations suggest that quadratus plantae is getting bulkier, implying its significance in human locomotion. Is it simply an accessory flexor that brings the line of pull of flexor digitorum longus in line with the long axis of the foot, as its name would suggest? We cite evidence from electromyographic studies that suggest it actually acts as a primary toe flexor in voluntary movements, being preferentially recruited over flexor digitorum longus. From comparative anatomical considerations it also seems likely that quadratus plantae is an intrinsic evertor of the foot. Eversion is an important evolutionary asset, especially in erect bipedalism. Human electromyographic experiments have yet to confirm this. However, they do suggest that quadratus plantae functions to resist extension of the toes during the stance phase of locomotion, which serves to increase the stability of the foot. Future electromyographic experiments may provide more information on the role of quadratus plantae in human locomotor evolution and in foot eversion in particular.

Origin and Insertion of Quadratus Plantae Muscle

It arises by two heads, which are separated from each other by the long plantar ligament: the medial or larger head is muscular, and is attached to the medial concave surface of the calcaneus, below the groove which lodges the tendon of the flexor hallucis longus; the lateral head, flat and tendinous, arises from the lateral border of the inferior surface of the calcaneus, in front of the lateral process of its tuberosity, and from the long plantar ligament.

The two portions join at an acute angle, and end in a flattened band which is inserted into the lateral margin and upper and under surfaces of the tendon of the flexor digitorum longus, forming a kind of groove, in which the tendon is lodged. It usually sends slips to those tendons of the Flexor digitorum longus which pass to the second, third, and fourth toes.

• Origin: Plantar surface of the calcaneus
• Insertion: Flexor digitorum longus tendon
• Action: Help flex the distal phalanges
• Blood Supply: Lateral plantar artery
• Innervation: Llateral plantar nerve

Function of Quadratus Plantae Muscle

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.

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