The soleus is a broad, flat muscle deep to the gastrocnemius in the calf. It arises from the upper fibula and the soleal line of the tibia and inserts on the calcaneus through the calcaneal (Achilles) tendon. The tibial nerve supplies it, and it plantarflexes the ankle whatever the position of the knee.
| Origin | Posterior aspect of the head and upper fibula, soleal line and medial border of the tibia, and the tendinous arch between them. |
|---|---|
| Insertion | Posterior surface of the calcaneus via the calcaneal tendon. |
| Innervation | Tibial nerve (S1-S2). |
| Blood supply | Posterior tibial and fibular arteries. |
| Action | Plantarflexes the ankle and stabilises the leg on the foot when standing. |
3D model: BodyParts3D (CC BY 4.0), adult male reference anatomy. Highlighted structure shown with nearby bones for context.
The soleus is rich in slow-twitch fibres and contracts constantly during standing. Its contractions squeeze the deep veins of the calf, so it acts as a peripheral venous pump.
The soleus crosses only the ankle, so it works with the knee bent or straight, while the gastrocnemius crosses the knee and the ankle.
The calcaneal (Achilles) tendon.
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