The ankle region consists of two important joints that enable us with activities such as walking, running and dancing. These are the ankle or talocrural joint and subtalar joint, which produce a myriad of movements such as plantar flexion/dorsiflexion, inversion/eversion, abduction/adduction. Those movements are possible thanks to the muscles of the leg whose tendons cross the various aspects of the ankle.
The leg muscles that move the ankle are grouped as follows:
- The anterior muscles of the leg - primarily dorsiflexion of the foot, aiding inversion and eversion of the foot.
- The posterior muscles of the leg - primarily plantar flexion of the foot, aiding inversion of the foot.
- The lateral muscles of the leg - eversion of the foot.
All of these muscles originate in the leg and insert somewhere within the foot. However, the foot itself has its own group of intrinsic muscles, which move the toes in various directions and allow finer coordination compared to the leg muscles.
The foot muscles are grouped either by layers (horizontal classification), or by groups (vertical classification). Following the layer organization, the foot muscles are divided superficial to deep:
- First layer: Abductor hallucis, flexor digitorum brevis, abductor digiti minimi
- Second layer: Quadratus plantae, lumbricals
- Third layer: Flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis
- Fourth layer: Plantar and dorsal interossei
When assessed by groups, the foot muscles are first divided into plantar and dorsal. The dorsal foot muscles are extensor digitorum brevis and extensor hallucis brevis muscles and their primary function is to extend the toes. The plantar muscles are further divided as follows:
- Lateral foot muscles: Abductor digiti minimi, flexor digiti minimi brevis and opponens digiti minimi muscles. They move the fifth toe.
- Central plantar muscles: Flexor digitorum brevis, quadratus plantae, lumbricals (4), plantar interossei (3) and dorsal interossei muscles (4). They move the lateral four toes.
- Medial plantar muscles: Abductor hallucis, adductor hallucis and flexor hallucis brevis muscles. They move the thumb (hallux).
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