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Soleus Muscle Anatomy

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Origin
  • Head of the fibula and posterior surface of the fibula
  • Soleal line and medial border of the tibia
Insertion
  • Posterior surface of the calcaneus via the calcaneal tendon
Action
  • Plantar flexes the foot at the ankle joint
Innervation
  • Tibial nerve (S1-S2)
Blood Supply
  • Popliteal artery
  • Fibular artery
  • Posterior tibial artery
Last updated: Estimated Reading Time: 5 min

Location & Overview

The soleus muscle is a muscle of the posterior lower leg and has the primary role of plantar flexion (extending the ankle). It is large and flat, located deep to the gastrocnemius muscle. It belongs to a pair of muscles referred to as the ‘calf muscles’. The official anatomical term for the calf muscles is the ‘triceps surae’. The triceps surae is composed of the gastrocnemius muscle and the soleus muscle. Some people also consider the plantaris muscle part of the calf muscles. The muscle bellies of the soleus and gastrocnemius muscles merge to form the calcaneal tendon as they approach the foot.[1,2]

The calcaneal tendon, which is formed by the soleus and gastrocnemius, is also known as the ‘Achilles tendon’. It is the thickest tendon in the human body. The plantaris muscle, though not a major contributor, can also be involved in the formation of the calcaneal tendon. In some people, the plantaris tendon is attached to the calcaneal tendon or runs alongside it before inserting onto the calcaneus (heel bone). However, the plantaris muscle is highly variable and may be absent entirely in some people (around 7–20% of people).[3,4]

Soleus muscle from an anterior view
Here, we can see the soleus muscle from an anterior view.
Soleus muscle from a posterolateral view
Here, we can see the soleus from a posterolateral view.
Soleus muscle, lateral view
Here, we can see the soleus from a lateral view.
Soleus muscle, medial view
Here, we can see the soleus from a medial view.
Soleus muscle highlighted in red among the other leg muscles
In this image, the soleus muscle is highlighted among the other muscles of the leg. For clear visibility, the gastrocnemius has been removed, allowing us to see the soleus unobstructed.

Origin & Insertion

The soleus muscle originates from the head of the fibula, the posterior surface of the fibula, the soleal line, and the medial border of the tibia. As the soleus muscle extends distally down the lower leg, it merges with the gastrocnemius muscle, forming the calcaneal tendon, also known as the Achilles tendon. This tendon then inserts into the posterior surface of the calcaneus.[5,3,1]

origin of the soleus muscle highlighted in red
Here, we can see the origin of the soleus muscle highlighted in red. The soleus originates from the head of the fibula, posterior surface of the fibula, soleal line of the tibia, and medial border of the tibia.
insertion of the soleus muscle highlighted in blue
Here, we can see the insertion of the soleus muscle highlighted in blue. The soleus inserts on the posterior surface of the calcaneus via the calcaneal tendon (also known as the Achilles tendon).

Action & Function

The soleus muscle can cause plantar flexion at the ankle joint. Plantar flexion involves extending the ankle joint (i.e. extending the foot away from the body or going onto your tiptoes). The soleus works together with the other calf muscles in activities such as running and jumping, where powerful push-off forces are required. In addition, the soleus plays a role in maintaining postural stability and balance while standing, as it helps resist the force of gravity and stops the body from falling forward.[5,3,1]

Image of a person demonstrating the movement of foot plantar flexion.
This image shows an example of foot plantar flexion, which involves extending the ankle. The opposite of plantar flexion is dorsiflexion. The soleus muscle’s primary action is plantar flexion.

Innervation

The soleus muscle is innervated by the tibial nerve (S1-S2). The tibial nerve is the larger terminal branch of the sciatic nerve, which divides into the tibial nerve and the common fibular nerve. It also provides innervation for other muscles of the posterior lower leg compartment (e.g. the gastrocnemius and plantaris).[1]

Image of the tibial nerve
Highlighted in red, we can see the tibial nerve, which is a branch of the sciatic nerve. The tibial nerve innervates the soleus muscle from the spinal nerve roots of S1 and S2. The tibial nerve also innervates the gastrocnemius and plantaris muscles.

Blood Supply

Blood is supplied to the soleus muscle via the popliteal, fibular, and posterior tibial arteries.[6]

Image of the arteries of the lower limb
This image shows the arteries of the lower limb.

References

  1. [1] Binstead JT, Munjal A, Varacallo M. Anatomy, Bony Pelvis and Lower Limb, Calf. (Updated 2021 Jun 3). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459362/
  2. [2] Kimura N, Kato K, Anetai H, Kawasaki Y, Miyaki T, Kudoh H, Sakai T, Ichimura K. Anatomical study of the soleus: Application to improved imaging diagnoses. Clin Anat. 2021 Oct;34(7):991-1001. doi: 10.1002/ca.23667. Epub 2020 Sep 2. PMID: 32783229.
  3. [3] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  4. [4] Simpson SL, Hertzog MS, Barja RH. The plantaris tendon graft: an ultrasound study. J Hand Surg (Am) 1991;16:708–711.
  5. [5] Mostafa E, Graefe S, Varacallo M. Anatomy, Bony Pelvis and Lower Limb, Leg Posterior Compartment. (Updated 2021 Jun 3). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537340/
  6. [6] Fathi M, Hassanzad Azar M, Arab Kheradmand A, Shahidi S. Anatomy of arterial supply of the soleus muscle. Acta Med Iran. 2011;49(4):237-40. PMID: 21713734.

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