Overview
This lecture covers the muscles of the leg, grouped by their anatomical location (anterior, lateral, and posterior), and explains their origins, insertions, and primary actions.
Anterior Leg Muscles
- Tibialis anterior originates from the lateral condyle of the tibia and inserts on the first cuneiform and base of first metatarsal.
- Its main actions: dorsiflexion, adduction, and medial rotation of the foot.
- Extensor digitorum longus starts at the lateral condyle of the tibia/head of fibula, splits into four tendons to dorsal phalanges.
- Main action: extends toes and dorsiflexes the foot.
- Extensor hallucis longus arises from the medial fibula and inserts on dorsal proximal/intermediate phalanx of big toe.
- Its main action: extension of the big toe.
- Peroneus tertius (anterior peroneal muscle) originates from distal fibula, inserts on the fifth metatarsal.
- Actions: foot abduction, external rotation, and dorsiflexion.
Lateral Leg Muscles
- Peroneus longus originates from head of fibula, passes under fibular retinaculum, inserts on base of first metatarsal and medial forefoot.
- Its actions: plantarflexion, external rotation, and abduction of the foot.
- Peroneus brevis arises from distal fibula, inserts on the fifth metatarsal tubercle.
- Actions: plantarflexion, extension, and lateral rotation of foot.
Posterior Leg Muscles
Superficial Group
- Triceps surae consists of gastrocnemius (two heads) and soleus muscles, inserting via the Achilles tendon on the calcaneus.
- Main action: plantarflexion of foot and extension of leg for walking.
- Plantaris runs between gastrocnemius and soleus, weakly assists triceps surae actions.
Deep Group
- Popliteus originates from lateral femoral epicondyle, inserts on posterior tibia.
- Actions: internal rotation and some flexion of the leg.
- Tibialis posterior starts at medial borders of tibia/fibula, inserts at navicular (scaphoid).
- Main actions: plantarflexion and internal rotation.
- Flexor digitorum longus originates from posterior tibia, divides into four tendons to distal phalanges of four toes.
- Action: flexes toes and foot.
- Flexor hallucis longus starts at posterior fibula, inserts at distal phalanx of big toe.
- Action: flexes big toe and foot.
Key Terms & Definitions
- Dorsiflexion — Upward movement of the foot toward the shin.
- Plantarflexion — Downward movement of the foot away from the shin.
- Abduction — Movement away from the midline of the body.
- Adduction — Movement toward the midline of the body.
- Retinaculum — Band of connective tissue holding tendons in place.
Action Items / Next Steps
- Review the origins, insertions, and actions of each muscle group.
- Study diagrams or 3D models to visualize muscle locations and attachments.