Hamstring Muscles


What are hamstring muscles?

Your hamstring muscles are skeletal muscles. They’re voluntary muscles, meaning you control how they move and work. You have three hamstring muscles at the back of your thigh. You use these muscles to walk, climb stairs, do squats and perform many other leg movements.

The hamstring muscles are very susceptible to injury, especially in athletes that run and sprint. Suddenly stopping, slowing down or changing direction puts a lot of strain on these muscles. Extending your leg when running can also overstretch these muscles. A hamstring injury is often called a “pulled hamstring.”


What is the purpose of the hamstring muscles?

Your hamstring muscles serve a variety of functions, including:

  • Bending the knee joint.
  • Extending the hip joint.
  • Rotating the hip joint.


Where are the hamstring muscles located?

Your hamstring muscles are located in the back of the thigh, starting at your hip and inserting to the knee. Hamstring tendons attach them to bones in your pelvis, knee and lower leg.

How are the hamstring muscles structured?

The three hamstring muscles are:

  • Biceps femoris, closest to the outside of your body. The function of this hamstring is to flex your knee, extend the thigh at your hip and rotate your lower leg from side-to-side when your knee is bent.
  • Semimembranosus, closest to the middle of your body. This hamstring flexes your knee joint, extends your thigh at your hip and offers medial rotation for your hip and lower leg.
  • Semitendinosus, between the semimembranous and the biceps femoris. The function of this hamstring matches that of the semimembranosus.

What are the hamstring muscles made of?

Your hamstring muscles contain thousands of tiny, elastic muscle fibers. These fibers help the muscles contract, or tighten. Muscle fibers are red and white. So, your hamstring muscles might look striated (striped) if you could see them under your skin.

Conditions and Disorders

What conditions and disorders affect hamstring muscles?

A hamstring muscle strain is the result of overstretched muscle fibers. Hamstring strains can range from mild to severe:

  • Grade 1: The muscle fibers overstretch, but don’t tear. You may feel mild hamstring muscle pain or swelling, but you can usually still use your leg.
  • Grade 2: One or more of your hamstring muscles is partially torn. Pain and swelling may prevent you from using your leg.
  • Grade 3: The muscle tissue completely tears away from tendon or bone. Sometimes the tendon even pulls a piece of bone away (avulsion). The swelling and pain are severe; you may have difficulty using your leg.

How common are hamstring muscle injuries?

Hamstring muscle injuries are the most common sports injury. One study suggests they account for about 37% of all soccer injuries.

Who gets hamstring muscle injuries?

Hamstring muscle injuries are common in athletes who run at fast speeds. This includes sprinters and people who play soccer, basketball and football. They can also occur in skiers, skaters, dancers and other athletes who often have their knees bent in deep squat positions.

You’re also at risk for hamstring muscle injuries if you:

  • Are a young athlete who is still growing.
  • Are over age 40.
  • Have had a previous hamstring injury.
  • Have hamstring muscle fatigue.
  • Have weak or tight hamstrings or quadriceps (muscles at the front of your thighs).
  • Do not perform proper warm up and stretches before activity.

What are the symptoms of hamstring muscle injuries?

Hamstring muscle injuries may cause:

  • An abnormal lump or indentation behind your thigh.
  • Bruising or discoloration on the back of your leg.
  • Burning or stinging behind your thigh, sometimes called gluteal sciatica.
  • Difficulty bearing weight on your leg.
  • Hamstring muscle weakness.
  • Inability to bend your knee, which may lead to walking with a stiff, straight leg.
  • Popping sensation at the back of the thigh.
  • Sudden, sharp pain in the back of your thigh.
  • Swelling right after the injury.


How can I keep my hamstring muscles healthy?

Take care of your hamstring muscles by:

  • Not pushing through hip, leg or knee pain.
  • Resting your hamstring muscles between workouts or periods of exertion.
  • Stretching and warming up your hamstring muscles properly before activity.

Frequently Asked Questions

When should I call my doctor?

Contact your doctor right away if you:

  • Can’t move your leg and pain in your thigh persists.
  • Experience ongoing difficulty with walking.
  • Experience numbness in your lower back, hips or legs.

A note from Cleveland Clinic

Your hamstring muscles play a vital role in helping you walk, run, bend your knees and extend your legs. But these muscles are also very susceptible to injury, especially if you play soccer or football — or do other activities that require a lot of quick stops and starts. While most hamstring muscle injuries heal with conservative treatments, some require surgery. You can take care of your hamstring muscles and reduce your risk of injury by incorporating proper warm up and stretches prior to physical activity. You should also rest your muscles if you feel pain or fatigue. More importantly, if pain persists in the back of your thigh, seek immediate attention.

Last reviewed by a Cleveland Clinic medical professional on 08/18/2021.


  • Dave HD, Shook M, Varacallo M. Anatomy, Skeletal Muscle. (https://www.ncbi.nlm.nih.gov/books/NBK537236/) [Updated 2020 Sep 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Accessed 11/3/2021.
  • Poudel B, Pandey S. Hamstring Injury. (https://www.ncbi.nlm.nih.gov/books/NBK558936/) [Updated 2020 Sep 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Accessed 11/3/2021.
  • American Academy of Orthopaedic Surgeons. Hamstring Muscle Injuries. (https://orthoinfo.aaos.org/en/diseases--conditions/hamstring-muscle-injuries) Accessed 11/3/2021.

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