Understanding the anatomy of the lower leg is important for athletes, physical therapists, and anyone interested in learning more about how the body works. Let's explore the function, origins, and insertion points of the bones and muscles involved in the lower leg.
Bones of the lower leg
The lower leg is the area between the knee and ankle. Two long bones; the tibia and the fibula, comprise the lower leg.
The tibia is the larger of the two bones and is located on the medial (inner) side of the leg. The fibula is located on the lateral (outer) side of the leg and is the smaller of the two bones. Together, these bones form the ankle joint.
Adjacent bones are the patella (knee cap), femur (upper leg bone), and the talus and calcaneus (bones of the hind foot).
Muscles of the lower leg
The muscles of the lower leg are divided into three compartments: anterior (front), lateral (side), and posterior (back). Each compartment contains several muscles that work together to produce movement.
Extensor Digitorum Longus
Extensor Digitorum Longus originates on the lateral condyle of the tibia and the proximal three-fourths of the fibula. It inserts on the extensor expansion of the toes, and is responsible for dorsiflexion and extension of the toes.
Extensor Hallucis Longus
Extensor Hallucis Longus originates on the middle part of the anterior surface of the fibula and the interosseous membrane. It inserts on the distal phalanx of the great toe. It is responsible for dorsiflexion and extension of the great toe.
The Fibularis (or Peroneus) Brevis muscle originates on the lower two-thirds of the lateral surface of the fibula. It inserts on the tuberosity of the fifth metatarsal. It is responsible for plantar flexion and eversion of the foot.
Fibularis (or Peroneus) Longus muscle originates on the head and upper two-thirds of the lateral surface of the fibula. It inserts on the plantar surface of the first metatarsal and the medial cuneiform. It is responsible for plantar flexion and eversion of the foot.
Fibularis (or Peroneus) Tertius originates on the distal third of the anterior surface of the fibula and the interosseous membrane. It inserts on the dorsal aspect of the base of the fifth metatarsal. It is responsible for dorsiflexion and eversion of the foot.
Gastrocnemius originates on the lateral and medial condyles of the femur. It inserts on the calcaneus via the Achilles tendon. It is responsible for plantar flexion of the foot and knee flexion. Fun fact: Gastrocnemius takes its name from 'gastro' meaning stomach, due to the muscle's shape.
Plantaris is a minor accessory muscle slightly involved with both knee and plantar flexion but not in a significant way. Believed to be a vestigial muscle, its function in modern man is served by the much more powerful gastrocnemius and soleus.
Popliteus is a small but major stabilising muscle of the knee. At different points of the walking movement, it rotates the fibula on the tibia, then vice versa. Along with tibialis posterior, flexor digitorum longus, and flexor hallucis longus, popliteus forms the deep posterior compartment of the leg.
Soleus originates on the proximal tibia and fibula, and inserts on the calcaneus via the Achilles tendon. It is responsible for plantar flexion of the foot.
Tibialis Anterior is the primary muscle on the anterior or front of the lower leg. It originates on the lateral surface of the tibia and the interosseous membrane. Tibialis Anterior inserts on the medial cuneiform and first metatarsal bones. It is responsible for dorsiflexion and inversion of the foot.
Tibialis Posterior is a deep muscle of the lower leg hidden from view by the superficial gastrocnemius and soleus muscles. This stocky muscle sits directly behind the tibia, and acts to plantarflex the foot and invert the foot and provides key support to the medial arch. Its origins are the posterior surface of tibia, posterior surface of fibula, and interosseous membrane. It inserts on the plantar surface of the foot.
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