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Leg Muscles - want to learn more about it?

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Leg Muscles

The muscles of the leg are important for movements of the ankle, and for adjustments to changing surfaces we are walking on.

There are three distinct groups i.e. an anterior group, a posterior group, and a lateral group.

The function of these compartments helps us in activities such as walking, kicking, running and dancing. It is important to consider muscle groups as functional units. The individual muscles in each compartment may have additional functions, but the primary function of each compartment is the most important thing to remember.

Key Facts
Anterior (dorsiflexor) compartment Muscles: tibialis anterior (inversion of the subtalar joint), extensor digitorum longus (extension of the 2nd-5th toes), extensor hallucis longus (extension of the hallux), fibularis tertius (dorsiflexion of the ankle)
Motor innervation: common fibular nerve
Vascularization: anterior tibial artery (branch of the popliteal artery)
Posterior (plantar flexor) compartment Superficial muscle group: gastrocnemius (plantar flexion of the ankle and flexion of the knee) and soleus (plantar flexion)
Deep muscle group: popliteus (lateral rotation of the tibia), flexor digitorum longus (flexion of the 2nd-5th toes), flexor hallucis longus (flexion of the hallux), tibialis posterior (plantarflexes the ankle, inverts the subtalar joint)
Motor innervation: tibial branch of the sciatic nerve
Vascularization: posterior tibial artery (branch of the popliteal artery)
Lateral (fibular) compartment Muscles: fibularis longus (maintains the lateral arch of the foot), fibularis brevis (everts the subtalar joint, plantarflexes the ankle)
Motor innervation: superficial branch of the common fibular nerve
Vascularization: fibular artery (branch of the posterior tibial artery)
Clinical relations Acute compartment syndrome, medial tibial stress syndrome, common fibular nerve palsy

In this article, we will discuss the gross anatomy, functional anatomy and clinical relevance of the leg muscles. 

Anatomy of the leg

Anatomically the leg is defined as the region of the lower limb below the knee. It consists of the posterior, anterior and lateral compartment. There is no medial compartment of the leg (unlike the thigh). The leg is innervated by branches of the sciatic nerve, and receives its blood supply from branches of the popliteal artery. Drainage also occurs from the popliteal vein, and superficial drainage from the small and great saphenous veins.

Anterior (Dorsiflexor) compartment

Muscles

This compartment contains the tibialis anterior, extensor digitorum longus, extensor hallucis longus and fibularis tertius.

  • Tibialis anterior muscle originates from the superior two-thirds of the lateral tibial condyle, and inserts onto the medial cuneiform and first metatarsal of the foot. Its action is inversion of the subtalar joint.
Recommended video: Functions of the tibialis anterior muscle
Functions and anatomy of the tibialis anterior muscle shown with 3D model animation.
  • Extensor digitorum longus muscle originates from the anterior tibial shaft, the superior three-quarters of the interosseus membrane, and the anterior surface of the lateral tibial condyle. It inserts onto the dorsal surface of the middle and distal phalanges of the lateral four toes. Its action is to extend the 2nd to 5th toes.

  • Extensor hallucis longus muscle arises from the central portion of the fibula, the interosseus membrane and inserts onto the dorsal surface of the distal phalanx of the hallux. Its action is to extend the hallux.
Recommended video: Functions of the extensor hallucis longus muscle
Functions and anatomy of the extensor hallucis longus muscle shown with 3D model animation.
  • Fibularis tertius muscle arises from the lower aspect of the fibular shaft and interosseus membrane and inserts onto the dorsal surface of the fifth metatarsal. Its action is to dorsiflex the ankle.

Motor innervation

The motor innervation to the anterior compartment comes from the deep branch of the common fibular nerve (ventral rami of L4-S2).

Blood supply

The blood supply of the anterior compartment is from the anterior tibial artery, a branch of the popliteal artery.

Recommended video: Neurovasculature of the lower leg and knee
Arteries, veins and nerves of the lower leg and knee.

Posterior (Plantarflexor) compartment

Superficial muscle group

This compartment is divided into a deep and superficial group. The superficial group contains the gastrocnemius and soleus muscles. They are also known as the ‘calf muscle pump’, which assists venous return to the heart as the veins of the leg run through the leg.

  • Gastrocnemius muscle is a large and strong plantar flexor of the ankle and flexor of the knee. It originates from the dorsal surfaces of the femoral condyles, above their articulating portion.
Recommended video: Functions of the gastrocnemius muscle
Functions and anatomy of the gastrocnemius muscle shown with 3D model animation.
  • Soleus muscle is deep to the gastrocnemius and is another plantar flexor. It arises from the fibula and soleal line on the dorsal surface of the tibia.
Recommended video: Functions of the soleus muscle
Functions and anatomy of the soleus muscle shown with 3D model animation.

Both the gastrocnemius and soleus muscles converge together to form the calcaneal tendon. This tendon then inserts onto the calcaneus tarsal bone, i.e. the heel bone.

Deep muscle group

The deep group consists of the popliteus, flexor digitorum longus, flexor hallucis longus and the tibialis posterior.

  • Popliteus muscle arises from the lateral femoral condyle and inserts onto the posterior shaft of the tibia above the soleal line. It causes lateral rotation of the tibia with respect to the femur (unlocks the knee), as the tibia undergoes medial rotation in terminal extension and the anterior cruciate ligament and extrinsic ligaments of the knee (medial collateral, lateral collateral) become taut.
Recommended video: Popliteus muscle
Origins, insertions, innervation and functions of the popliteus muscle.
  • Flexor digitorum longus muscle arises from the proximal shaft of the tibia and inserts onto the plantar surface of the distal phalanges of the lateral four toes.
Recommended video: Functions of the flexor digitorum longus muscle
Functions and anatomy of the flexor digitorum longus muscle shown with 3D model animation.
  • Flexor hallucis longus muscle arises from the dorsal surface of the middle third of the fibula and inserts onto the plantar surface of the base of the distal phalanx of the hallux. The long flexor muscles flex their respective digits.
Recommended video: Functions of the flexor hallucis longus muscle
Functions and anatomy of the flexor hallucis longus muscle shown with 3D model animation.
  • Tibialis posterior muscle arises from adjacent parts of the tibia and fibula and medial cuneiform and navicular bone. It plantarflexes the ankle and inverts the subtalar joint.
Recommended video: Functions of the tibialis posterior muscle
Functions and anatomy of the tibialis posterior muscle shown with 3D model animation.

Motor innervation

The motor innervation to the posterior compartment comes from the tibial branch of the sciatic nerve (ventral rami of L4-S3). The muscles of this compartment cause plantar flexion. The tibialis posterior also acts to invert the subtalar joint.

Blood supply

The blood supply to the posterior compartment is from the posterior tibial artery, a branch of the popliteal artery.

Lateral (Fibular) compartment

Muscles

This compartment consists of the fibularis longus and fibularis brevis muscles.

  • Fibularis longus muscle arises from superior lateral shaft of the fibula. Its tendon runs around the lateral aspect of the cuboid bone, runs in a tunnel formed by the long plantar ligament against the inferior surface of the cuboid bone, and eventually inserts onto the first metatarsal and medial cuneiform. It maintains the lateral arch of the foot in this regard.
Recommended video: Functions of the fibularis longus muscle
Functions and anatomy of the fibularis longus muscle shown with 3D model animation.
  • Fibularis brevis muscle arises from lower two thirds on the lateral surface of the fibula and inserts onto the 5th metatarsal.
Recommended video: Functions of the fibularis brevis muscle
Functions and anatomy of the fibularis brevis muscle shown with 3D model animation.

Both these muscles evert the subtalar joint, and plantar flex the ankle (talocrural joint). Inversion and eversion of the ankle is important for our adjustment when walking on uneven surfaces.

Motor innervation

The motor innervation to the lateral compartment comes from the superficial branch of the common fibular nerve (ventral rami of L4-S2).

Blood supply

The blood supply to the lateral compartment is from the fibular artery, a branch of the posterior tibial artery.

Clinical Points

Acute compartment syndromeThis is a condition in which the pressure in a closed compartment increases to such extent that the microcirculation of the tissues in that compartment is diminished. The resulting inadequate perfusion and oxygenation leads to soft tissue ischemia, anoxia and cell death, especially in skeletal muscle. The most common site of compartment syndrome is the leg. Risk factors include the following:

  • age
  • gender
  • trauma, especially the type and site
  • revascularization after acute arterial injury or obstruction
  • incorrect limb positioning during prolonged surgical procedures
  • excessive exercise

Shin Splints/Medial tibial stress syndrome: If the anterior compartment of the leg is repetitively used, the anterior shin adjacent to the tibia becomes painful. This condition is known as shin splints, and commonly affects athletes who engage in running or jumping. It usually affects the middle or lower third of the medial side of the tibia.

Common Fibular Nerve palsy: The common fibular nerve (L4-S2) winds around the neck of the fibula, and divides into the deep and superficial fibular nerves. The nerve runs close to the skin as it winds around the neck of the fibula, and is hence vulnerable to compression from tight clothing or casts on the leg. Symptoms of this nerve palsy include:

  • foot drop 
  • loss of sensation over the anterior and lateral surface of the leg, and the dorsum of the foot.

Leg Muscles - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 921,002 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Frank H.Netter MD: Atlas of Human Anatomy, 5th Edition, Elsevier Saunders.
  • Chummy S.Sinnatamby: Last’s Anatomy Regional and Applied, 12th Edition, Churchill Livingstone Elsevier.
  • Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, 2nd Edition, Churchill Livingstone Elsevier.
  • Shin splints. NHS Choices (accessed 10/03/2016).
  • Jones O: The Common Fibular Nerve. TeachMeAnatomy.info (accessed 10/03/2016).
  • Wheeless C, MD: Peroneal Nerve. Wheeless' Textbook of Orthopaedics (accessed 10/03/2016)
  • Raza, H. and A. Mahapatra, Acute compartment syndrome in orthopedics: causes, diagnosis, and management. Adv Orthop, 2015. 2015: p. 543412.

Author, Review and Layout:

  • Shahab Shahid
  • Jérôme Goffin
  • Catarina Chaves

Illustrators:

  • First Illustration Gallery - Irina Munstermann
  • Second Illustration Gallery - Liene Znotina
  • Third Illustration Gallery - Begona Rodriguez, Liene Znotina
  • Fourth Illustration Gallery - Liene Znotina
  • Extensor hallucis longus muscle - anterior view - Liene Znotina
  • Gastrocnemius muscle - posterior view - Liene Znotina
  • Fibularis longus muscle - anterior view - Liene Znotina
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the leg and knee

Main muscles of the lower extremity

Tibia and fibula

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