Muscles abducting the toes

Abductor hallucis

Abductor digiti minimi

Dorsal interossei

Abductor hallucis

Abductor hallucis is a powerful and important muscle found superficially on the medial side of the plantar aspect of the foot, lying deep to the medial part of the plantar aponeurosis. It arises, in part, from the plantar aponeurosis, the plantar aspect of the medial tubercle of the calcaneus, the flexor retinaculum and the intermuscular septum separating it from flexor digitorum brevis.

The fibres pass forwards forming a tendon which passes over the medial side of the metatarsophalangeal joint of the great toe, to insert into the medial side of he base of the proximal phalanx in conjunction with the tendon of the flexor hallucis brevis.

Nerve supply

Abductor hallucis is supplied by the medial plantar nerve, root value S1, 2, with the skin covering the muscle supplied by root L5.

Action

As its name implies, the muscle abducts the great toe at the metatarsophalangeal joint and also helps to flex it at this point.

Functional activity

Abduction of the great toe is not of importance as such, except perhaps as a party trick and then very few people are able to perform the action easily! However, the muscle is strong and bulky, and it must therefore be assumed that it has an important role to play in some specific activity.

Due to its position along the medial side of the foot, together with the fact that it is attached at the back and front of the medial longitudinal arch, it can act as a bow-string to the arch when the foot is being used for propelling the body forwards. Its attachment to the medial side of the great toe also helps in controlling the central position of this toe when it is being flexed.

It should be noted that when the muscle contracts hard, the great toe does indeed move medially, but more importantly, the foot is positioned laterally, thus improving the relationship between great toe and medial side of the foot. Indeed, if this alignment of the foot and toes was encouraged from an early age many deformities of the toes may be prevented.

Palpation

Place the fingers on the medial plantar aspect of the foot, under the medial longitudinal arch. The toes are then flexed and the belly of the muscle can be easily palpated towards the heel. Tracing forwards from the heel, the tendon of the muscle can be felt.

Abductor digiti minimi

Abductor digiti minimi is found on the lateral side of the plantar aspect of the foot, lying deep to the plantar aponeurosis from which it gains part of its attachment. It also arises from the medial and lateral tubercles of the calcaneus and from the area between, as well as the intermuscular septum is separating it from flexor digitorum brevis.

The fibres pass forwards forming a tendon which inserts into the lateral side of the base of the proximal phalanx of the fifth toe.

Nerve supply

Abductor digiti minimi is supplied by the lateral plantar nerve, root value S2, 3, with the skin covering the muscle being supplied by root S1.

Action

On contraction abductor digiti minimi abducts the fifth toe at the metatarsophalangeal joint and also helps to flex it at this joint.

Functional activity

Because the muscle runs from the posterior to the anterior parts of the lateral longitudinal arch, it acts as a bow-string to this arch in a similar way to abductor hallucis on the medial side of the foot, except of course that the lateral arch can hardly be called a true arch. Nevertheless, the muscle certainly comes into action in running and jumping activities to ensure that this arch is maintained under stress.

Palpation

Unless a subject can abduct the fifth toe easily, the muscle is difficult to palpate.