Soleus Muscle Anatomy & Function

The Soleus muscle is a large muscle, flatter than the gastrocnemius, that is named for its resemblance to a sole, the flat fish that reclines on its side on the sea floor. The soleus is located deep to the gastrocnemius and is the “workhorse” of plantarflexion. It’s one of the superficial group of calf muscles.

The superficial group of calf muscles (muscles forming prominence of “calf” of posterior leg) includes the gastrocnemius, soleus, and plantaris.

The gastrocnemius and soleus muscles share a common tendon, the calcaneal tendon, which attaches to the calcaneus. Collectively, these two muscles make up the three-headed triceps surae (L. sura, calf). This powerful muscular mass tugs on the lever provided by the calcaneal tuberosity, elevating the heel and thus depressing the forefoot, generating as much as 93% of the plantarflexion force.

See Also: Plantaris Muscle
See Also: Gastrocnemius Muscle

Soleus Muscle Anatomy

The Soleus muscle has a continuous proximal attachment in the shape of an inverted U to the posterior aspects of the fibula and tibia and a tendinous arch between them, the tendinous arch of soleus (L. arcus tendineus soleus). The popliteal artery and tibial nerve exit the popliteal fossa by passing through this arch, the popliteal artery simultaneously bifurcating into its terminal branches, the anterior and posterior tibial arteries.

The Soleus muscle can be palpated on each side of the gastrocnemius when the individual is “standing on their toes” (weight on forefoot with ankle plantarflexed). The soleus may act with the gastrocnemius in plantarflexing the ankle joint; it cannot act on the knee joint and acts alone to produce plantarflexion when the knee is flexed (e.g., doing a squat or “duck walk”).

Soleus muscle has many parts, each with fiber bundles coursing in different direction. When the foot is planted, the soleus pulls posteriorly on the bones of the leg. This is important to standing because the line of gravity passes anterior to the leg’s bony axis. The soleus is thus an antigravity muscle (the predominant plantar flexor for standing and strolling), which contracts antagonistically but cooperatively (alternately) with the dorsiflexor muscles of the leg to maintain balance.

Composed largely of red, fatigue-resistant, slow-twitch (type 1) muscle fibers, it is a strong but relatively slow plantar flexor of the ankle joint, capable of sustained contraction. Electromyography (EMG) studies show that during symmetrical standing, the soleus muscle is continuously active.

References & More

1. Clinically Oriented Anatomy – 8th Edition
2. Binstead JT, Munjal A, Varacallo M. Anatomy, Bony Pelvis and Lower Limb: Calf. [Updated 2023 May 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459362/