Lateral Muscles of the sole of the Foot
Anatomy and supply
The lateral chamber formed by the plantar fascia contains three muscles. Their muscle bellies form the surface of the lateral foot sole (ball of the little toe). They are all innervated by the lateral plantar nerve (S1-S2), a branch of the tibial nerve. The following muscles lie within the lateral chamber:
- Abductor digiti minimi muscle: originates at the calcaneal tuberosity and plantar aponeurosis and inserts at the proximal phalanx and metatarsal bone of the little toe.
- Flexor digiti minimi brevis muscle: runs from the metatarsal bone of the little toe and long plantar ligament to the proximal phalanx of the little toe.
- Opponens digiti minimi muscle: originates at the long plantar ligament, the basis of the fifth metatarsal bone and the tendon sheath of the fibularis longus muscle. Thereupon it inserts again at the lateral border of the fifth metatarsal bone. This muscle is not found in all human bodies.
Besides the above mentioned muscles there are more structures lying within the lateral chamber of the plantar fascia supplying the lateral foot sole (lateral plantar artery, vein and nerve).
The lateral muscles of the foot sole move the little toe through flexion (abductor digiti minimi and flexor digiti minimi brevis muscle), abduction (abductor digiti minimi muscle) and opposition (opponens digiti minimi muscle). Furthermore they actively support the longitudinal arch of the foot sole. However in comparison to the medial muscles of the foot sole they are poorly developed and have a relatively little importance.