The Anatomy of the Soleus Muscle

The soleus is a large muscle on the back of your lower leg. This powerful muscle arises from the back of your shin bone and attaches to your heel bone as part of the Achilles tendon. The soleus muscle is active during activities like walking, running, and jumping. Injury to the soleus may affect your ability to perform these basic but necessary functions. The word soleus comes from the Latin term "solea," which means sandal. You have two soleus muscles located in each lower leg.

Anatomy

The soleus muscle originates from the back side of your upper tibia, or shin bone. Small slips of the muscle also arise from your fibular head and along the thin aponeurosis between your fibula and tibia. (An aponeurosis is a pearly white sheet of fascia that connects between two bones, serving to be an attachment point for muscles that require a large surface area.)

The soleus muscle courses down the back of your lower leg and is located just beneath your larger gastrocnemius muscle. The two muscles join together at the Achilles tendon and insert on the back side of your heel bone, called the calcaneus. Many professionals consider the two heads of the gastrocnemius (calf muscle) and the single soleus to be one muscle group called the triceps surae.

Your soleus muscles are innervated by the tibial nerves arising from the first and second sacral level in your lower spine.

Function

The soleus muscles function to plantar flex your foot. Plantar flexion is the direction of motion that occurs as your foot and toes point down. The soleus works with your calf muscle to accomplish this task.

The gastrocnemius, a two-joint muscle, crosses your knee and your ankle. It is an active plantar flexor of the ankle when your knee is straight. The soleus, on the other hand, is a single joint muscle, crossing only the ankle. When your knee is bent, the gastrocnemius muscle is placed on slack and is not able to forcefully contract to plantar flex your ankle. The soleus is very active as an ankle plantar flexor when your knee is bent.

Your soleus muscle gets stretched a bit as you are walking and ascending and descending stairs. It also is placed on stretch during running and activities that require jumping and hopping. When this muscle is stretched, it stores energy which is then released when the muscle contracts and shortens.

When you stand on one foot, the soleus muscle helps maintain proper balance. Since it is composed of mostly slow-twitch muscle fibers, it has high endurance and is able to withstand contractions and workloads for a prolonged period of time.

The soleus muscle also functions to help pump blood from your lower leg back to your heart. Your veins carry blood from your body to your heart. Inside these veins are small "one-way" valves. When your soleus muscle contracts, it acts like a sponge, pushing blood through your veins.

The one-way valves prevent blood from pooling back down into your lower leg. The action of the muscles acting as spongy pumps is often referred to as the skeletal muscle pump.

Associated Conditions

The strong soleus is responsible for much of the workload of your lower leg and thus is subject to possible injury. Common injuries to the soleus include:

• Muscle strains
• Achilles tendon tears
• Achilles tendonitis
• Compartment syndrome
• Muscle cramps
• Sever's disease (tightness in your calf and soleus that pulls abnormally on your heel bone)

An injury to your soleus muscle often results in certain signs and symptoms. These may include:

• Pain in your lower leg
• Swelling in your leg
• Difficulty standing and walking
• Bruising in your lower leg
• Tightness and cramping in your leg or legs

Deep Vein Thrombosis (DVT)

The large vein that courses between your soleus and calf muscles may also be the site of deep vein thrombosis (DVT). This condition occurs when a clot blocks the flow of blood from your lower leg to your heart. If the clot travels through your venous return system and into your lungs, the condition, called a pulmonary embolus, can be fatal.

Symptoms of a DVT may include:

• Pain in your lower leg
• Redness and swelling
• Cramping feeling your leg
• Warmth to touch

If you have any of these symptoms, visit your healthcare provider or emergency room right away. A simple ultrasound test can be done to rule out (or in) a DVT.

Once your healthcare provider diagnoses a condition with your soleus and lower leg, it may be time to start the rehabilitation process to help you return to full function.

Rehabilitation

Injuries to your soleus may vary in intensity, and thus your rehab considerations may vary as well.

In general, the early phase of healing after a soleus injury may involve a few weeks of immobilization with a brace or walking boot. This immobilization allows for the soleus muscle to heal and minimizes stress to your injured muscle.

Keep in mind that periods of immobilization often cause secondary problems of tight muscles, loss of range of motion, and weakness in the muscle groups that were immobilized.

Once immobilization of your soleus has occurred for two to four weeks, it may be time to get things moving again. Your local physical therapist (PT) is a good resource to help you properly rehab a soleus injury.

All of these goals should focus on helping you return to normal walking and running function.

Various treatments are available for rehabbing a soleus injury. Your PT can help determine the best ones for you. Be sure to check in with your PT or healthcare provider before starting any exercise program or rehabilitation for an injured soleus or lower leg.

Massage

Massage techniques may be used as part of your soleus physical therapy treatment. Massage helps to improve local blood flow, increase tissue extensibility, and decrease pain. Massage may also be used to manually push fluid away from your lower leg in attempts to decrease swelling.

Heat and Ice

After a soleus injury, heat may be applied to decrease pain and improve blood flow to the muscle. Heat promotes circulation, and may help bring in blood and nutrients to the injured tissue.

Ice is often used in the case of acute soleus strains and Achilles tears to decrease swelling and minimize pain and inflammation.

Ultrasound

Ultrasound is a deep heating modality occasionally used in physical therapy. It may be used to improve local blood flow, increase tissue flexibility, and speed cellular mechanisms to promote healing.

Care should be taken though; ultrasound use in PT has fallen under heavy scrutiny due to the lack of high-power studies supporting its use.

Electrical Stimulation

Electrical stimulation (e-stim) to your lower leg may be used to decrease pain that may occur with a soleus injury. The e-stim may also decrease swelling around your lower leg.

Kinesiology Taping

A newer treatment for musculoskeletal injuries is called kinesiology taping. This involves placing strips of cloth tape over your injured body part. The tape serves different functions depending on how it is placed and how much tension is on the tape.

Kinesiology taping is often used to improve muscle function, decrease pain and spasm, or decrease bruising after a muscle injury.

Stretching and Flexibility Exercises

An important component of soleus injury rehab is to improve the flexibility and mobility of the muscle. Exercises to improve soleus flexiblity may include:

• The towel calf stretch (with your knee bent)
• The runners stretch with your knees bent
• The bent knee stair hang

Keeping your knees bent during these stretching exercises ensures that the calf is kept on slack and the focus of the stretch is on your soleus.

When performing each stretch, hold the stretched position for 30 seconds, and be sure to stop if you feel any increasing pain in your calf and lower leg.

Strengthening Exercises

After a soleus injury, your rehab should focus on increasing the load-bearing tolerance of the muscle. This involves strengthening exercises for your lower legs and soleus.

Some exercises to strengthen your soleus may include:

• Bent knee plantar flexion with a resistance band
• Bent knee heel raises (as per the Alfredson protocol)
• Seated calf raises

Again, the bent knee position keeps your calf on slack and focus the workload on the soleus muscles of your lower legs.

Strengthening exercises are done for 10 to 20 repetitions, and you must stop if you feel any increase in pain.

Balance and Proprioception Exercises

Exercises to improve your balance can ensure that your soleus performs its job of stabilizing your lower leg properly. Exercises for balance may include:

• Single leg standing
• BAPS board
• BOSU training
• Tandem walking

You can expect the rehab for a soleus injury to take about four to eight weeks. Some courses of recovery are a bit shorter or longer depending on the severity of your injury.

A Word From Verywell

The soleus is a powerful muscle that courses down the back of your lower leg and attaches to your heel bone as a part of the Achilles tendon. Injury to the soleus may result in pain and limited walking and running ability. Understanding the anatomy of the muscle, along with possible injuries and rehab guidelines, can help you keep your soleus healthy and functioning properly.