Overview
This lecture covers the key muscles influencing the ankle joint, including their anatomical roles, nerve supply, and related clinical conditions.
Dorsiflexors of the Ankle
- Main dorsiflexor muscles: tibialis anterior, extensor digitorum longus, and extensor hallucis longus.
- Dorsiflexors are located on the anterior aspect of the leg and lift the foot upwards.
- These muscles are innervated by the deep peroneal (fibular) nerve.
- Foot drop commonly results from damage to the deep peroneal nerve due to spinal issues, peripheral nerve palsy near the fibula head, or rarely by central causes like stroke.
Plantarflexors of the Ankle
- Key plantarflexors: tibialis posterior, flexor digitorum longus, flexor hallucis longus, and triceps surae (gastrocnemius, soleus, and sometimes plantaris).
- Located on the posterior lower leg, these muscles point the foot downward.
- Tibialis posterior, flexor digitorum longus, and flexor hallucis longus pass through the tarsal tunnel, medial to the ankle.
- Gastrocnemius and soleus insert into the Achilles tendon.
- Relevant conditions: Achilles tendinopathy (pain at tendon’s midsection or insertion) and Achilles tendon rupture (requires urgent management).
Ankle Inversion Muscles
- Muscles causing inversion: tibialis anterior, tibialis posterior, flexor digitorum longus, and flexor hallucis longus.
- These muscles attach medially and contract to turn the foot inward.
Ankle Eversion Muscles
- Main everters: fibularis longus, fibularis brevis, and fibularis tertius (also called peroneus longus, brevis, and tertius).
- Fibularis longus and brevis run posterior to the fibula, looping under the lateral malleolus.
- Fibularis tertius runs anterior to the fibula and inserts into the fifth metatarsal.
- Fibularis longus and brevis assist in plantarflexion; fibularis tertius assists in dorsiflexion.
Nerve Supply to Ankle Muscles
- Fibularis longus and brevis are innervated by the superficial fibular nerve.
- Fibularis tertius is innervated by the deep fibular nerve.
- Remember: anterior muscles (including fibularis tertius) have deep innervation; lateral muscles have superficial.
Key Terms & Definitions
- Dorsiflexion — movement lifting the foot upwards toward the shin.
- Plantarflexion — movement pointing the foot downward.
- Inversion — turning the sole of the foot inward.
- Eversion — turning the sole of the foot outward.
- Tarsal Tunnel — space on the medial side of the ankle through which some flexor tendons pass.
- Achilles Tendon — strong tendon connecting gastrocnemius and soleus to the heel bone.
Action Items / Next Steps
- Review nerve supply and clinical conditions for each muscle group.
- Practice identifying muscle locations and actions with diagrams.
- Be able to explain the clinical relevance of common ankle injuries such as foot drop and Achilles tendon rupture.