Muscles of the Lower Extremity

Learning Objectives

  • Define action, origin, and insertion of listed muscles.

  • Identify locations of listed muscles relative to other structures.

  • Recognize synonyms and antagonists of muscles.

Anterior Compartment of the Thigh (Hip Action)

  • Sartorius: Origin - Anterior superior iliac spine; Insertion - Anteromedial surface of upper tibia. Action: Flexes, abducts, laterally rotates thigh; flexes leg.

  • Iliopsoas: Prime mover of thigh flexion.

Medial Compartment of the Thigh (Hip Action)

  • Pectineus: Adducts, flexes, medially rotates thigh.

  • Adductor brevis/longus/magnus: Adducts, flexes, medially rotates thigh; Adductor magnus also extends thigh (hamstring part).

  • Gracilis: Adducts thigh; flexes, medially rotates leg.

Posterior Compartment of the Thigh (Hip Action)

  • Gluteus maximus: Abducts, laterally rotates, extends thigh (prime mover of thigh extension).

  • Gluteus medius/minimus: Abducts and medially rotates thigh; stabilize pelvis during walking.

  • Piriformis: Laterally rotates thigh.

Anterior Compartment of the Leg

  • Tibialis anterior: Inverts, dorsiflexes foot (prime mover of dorsiflexion).

  • Extensor hallucis longus: Extends great toe; dorsiflexes foot.

  • Extensor digitorum longus: Extends toes 2-5; dorsiflexes foot.

  • Fibularis longus/brevis: Plantar flexes and everts foot.

Posterior Compartment of the Leg (Superficial Muscles)

  • Gastrocnemius: Origin - Lateral and medial condyles of femur; Insertion - Calcaneus via calcaneal tendon. Action: Flexes leg; plantar flexes foot.

  • Soleus: Origin - Head/proximal shaft of fibula; medial border of tibia; Insertion - Calcaneus via calcaneal tendon. Action: Plantar flexes foot.

  • Plantaris: Weakly flexes leg; plantar flexes foot.

Posterior Compartment of the Leg (Deep Muscles)

  • Tibialis posterior: Plantar flexes, inverts foot.

  • Flexor digitorum longus: Plantar flexes, inverts foot; flexes toes 2-5.

  • Flexor hallucis longus: Plantar flexes, inverts foot; flexes great toe.

  • Popliteus: Flexes, medially rotates leg unlock knee from full extension.

Lateral Compartment of the Leg

  • Contains plantar flexors and evertors of the foot.