The Anatomy of the Gastrocnemius Muscle

The anatomy and function of your calf muscle

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The gastrocnemius muscle, commonly known as the calf, is a large muscle located in the back of your lower leg. This muscle is an important mover of your lower leg and is responsible for normal walking and running actions. The gastrocnemius joins the soleus to form the Achilles tendon, the large tendon that attaches to your heel bone. You have two gastrocs, one in each lower leg.

Anatomy

The gastrocnemius muscle originates as two heads behind your knee. The medial, or inside, head arises from the medial condyle of the back of your femur (thigh bone). The lateral head on the outside part of your lower leg arises from the lateral condyle of your femur.

The muscle then courses down the back of your leg and joins the deeper soleus muscle. They both form the Achilles tendon and attach on the posterior aspect of your calcaneus, or heel bone. Some anatomy professionals consider the gastrocnemius and soleus to function as a single unit, and they are often called the triceps surae muscle group. (Triceps means three, and surae relates to the calf muscle.)

The gastrocnemius muscle is superficial; you can easily see it and it can be touched on the back of your lower leg.

It is interesting to note that a small sesamoid or floating bone called a fabella is present in the lateral aspect of the gastrocnemius in approximately ten to thirty percent of people. This anatomical variance usually causes no functional problems.

The gastrocnemius muscle is innervated by a nerve called the tibial nerve. It arises from the large sciatic nerve. The tibial portion is mainly served by the first and second sacral nerves from your lower back. Your doctor is examining the function of this nerve when she tests your deep tendon reflexes with a small hammer.

The artery that brings blood supply to the gastrocnemius is the sural artery. This artery arises from the popliteal artery behind your knee.

Function

The main function of the gastrocnemius muscle is to plantarflex your ankle. This means that as your gastroc contracts, your ankle and toes point down. When walking, running, or climbing stairs, the muscle works to flex your ankle and propel you forward.

The muscle is considered one of the "anti-gravity" muscles. It works along with the quadriceps and gluteus muscles to help raise our bodies up against the force of gravity. When your foot is planted on the ground, the gastrocnemius also acts to stabilize your foot and ankle.

Since the gastrocnemius crosses the knee joint in the back, it is considered a two joint muscle. Therefore, it not only acts on the ankle but the knee as well. The function of the gastroc at the knee is to work with your hamstrings to flex, or bend, your knee joint.

Because it is a two joint muscle, the gastrocnemius is prone to quite a bit of use, and overuse, while functioning. This can lead to problems with the muscle.

Conditions

Quite a few conditions can affect the calf muscles of your lower legs. These may include:

  • Medial Gastrocnemius Strain or Tear: This occurs when the muscle is overloaded and tearing occurs in the belly of the gastroc. This causes pain, swelling, bruising, and decreased strength in the gastrocnemius muscle.
  • Achilles Tendonitis: Your Achilles tendon may become irritated due to faulty foot and leg mechanics or due to overloading the tendon repetitively. When this occurs, Achilles tendonitis may result. The hallmark of Achilles tendonitis is exquisite pain in the tendon behind your heel bone, difficulty walking or running, and swelling near the Achilles tendon behind your lower leg.
  • Achilles Rupture: If your calf muscle and Achilles tendon are suddenly overloaded and cannot adequately manage the force, an Achilles rupture may occur. Tearing through your Achilles tendon may be partial or full. When this happens, you will likely experience pain, swelling, and difficulty walking. Typically, but not always, an Achilles tendon rupture results in surgery to fix the problem.
  • Calf Spasms: Many people are prone to getting calf spasms. These sudden, tight and squeezing sensations in your gastrocnemius may occur randomly. It remains a mystery the cause of gastroc spasms, but many people theorize they occur due to water and electrolyte imbalance in your muscular system.
  • Paralysis or Weakness Due to Tibial Nerve Injury: If you have back pain and sciatica, the nerve that travels to your gastrocnemius may become pinched. This may be due to foraminal stenosis or a herniated disc in your back. The pinched nerve decreases signals to your gastrocnemius from your brain, and this may result in weakness or paralysis of the muscle. You may have difficulty contracting the muscle to walk, and you may notice significant atrophy, or shrinking, of your gastrocnemius.

If you have pain or limited mobility in your gastrocnemius, it is important to see your doctor. He or she can diagnose your condition and help get you on track to recovery.

Rehabilitation

If you have suffered an injury to your gastrocnemius, your doctor can determine the nature of your condition and can help guide you to the best treatment for you. Working with a physical therapist may be a good idea to help with various gastrocnemius injuries.

Initial treatment for many gastrocnemius injuries typically includes a period of rest or immobilization. This allows your calf muscle to heal so you can start restoring flexibility and strength to the muscle. Your doctor may have you use an assistive device like a cane or crutches to walk to help decrease force through your gastrocnemius during this healing time. Once a short period of rest is complete, rehabilitation to your calf can begin.

Rehab for your gastrocnemius depends on the severity and type of injury you have suffered, and your PT will likely use various treatments to help you fully recover. These may include:

  • Massage: Massage for your gastrocnemius muscles can help improve local blood flow, tissue extensibility, and relieve pain and spasms. It is often used as a treatment for a calf strain or tear, calf spasms, and Achilles tendonitis. A specific type of massage called scar tissue mobilization may be utilized if you have had surgery to your calf or Achilles. This can help improve tissue mobility around the scar that has formed.
  • Gastrocnemius Stretching: Improving flexibility to your gastrocnemius muscles may be a component of your rehab. Stretches like the towel calf stretch or the runner's stretch can help improve gastroc flexibility and mobility around your ankle and knee. Stretches for your calf can also help alleviate muscle spasms. Most stretching exercises are held for 15 to 30 seconds and can be performed several times each day.
  • Kinesiology Taping: Your PT may perform taping to your gastrocnemius muscle as part of your injury rehab. Kinesiology tape may help to decrease pain and improve the way your gastroc contracts to support your ankle and knee.
  • Strengthening Exercises: Working on gastroc strength may be an important component of your injury rehab. If you have weakness due to a pinched nerve, you may perform exercises for your back to relieve pressure off the nerve. Then, you may work to strengthen the calf muscle. Strengthening your calf after a strain may also be warranted. Exercises like ankle plantar flexion with a resistance band may be done, or you can perform heel raises on a step to help strengthen the gastroc. A specific program for the gastrocnemius and soleus muscle group is called the Alfredson protocol. This involves using eccentric exercises to adequately load the calf and Achilles tendon to prevent problems like Achilles tendonitis.
  • Physical Modalities: Your PT may use heat or ultrasound as another treatment option. Heat improves blood flow to the muscle, and a deep heating treatment called ultrasound may be used. Ultrasound penetrates into your gastroc muscle belly and improves blood flow and tissue mobility there. Care should be used though; many studies have shown that there is little therapeutic benefit to ultrasound and that it may not be any more effective than simply exercising the muscle to improve circulation.
  • Balance Exercises: Your gastrocnemius is a major stabilizer of the lower extremity, and it is active when your foot is planted on the ground to stabilize your leg. Performing balance exercises may help improve gastroc function to get you back to normal walking and running. Exercises like the single leg stance may be done. Using a BAPS board or wobble board can also be helpful, and standing on a BOSU ball can improve balance and gastrocnemius function.

Recovery from a gastrocnemius injury can take anywhere from two to twelve weeks depending on the severity of the injury. Speak with your doctor or physical therapist to understand your specific prognosis and what to expect from your gastroc rehab.

A Word From Verywell

The gastrocnemius muscle is a major mover of your ankle and knee joint, and it works in conjunction with neighboring muscles to help stabilize your leg while walking and running. It is also prone to various injuries and conditions. Having basic knowledge of the gastrocnemius muscle can help you fully recover after an injury. That way, you can quickly get back to your normal activity and function.

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  • Andjelkov K, Atanasijevic TC, Popovic VM, Sforza M, Atkinson CJ, Soldatovic I. Anatomical aspects of the gastrocnemius muscles: A study in 47 fresh cadavers. J Plast Reconstr Aesthet Surg. 2016;69(8):1102-8. doi:10.1016/j.bjps.2016.04.002