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 thigh muscles to walk, climb stairs, run, do squats and perform many other leg movements.

Hamstring muscles are very susceptible to injury, especially in athletes who 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 common hamstring injury is called a “pulled hamstring” or strain.

What is the purpose of your hamstring?

Your hamstring muscles serve a variety of functions, including:

• Bending your knee joint
• Extending your hip joint
• Rotating your hip joint

Where are your hamstring muscles located?

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

How are your hamstring muscles structured?

The three hamstring muscles are:

• Biceps femoris. This muscle is on the outside of the back of your thigh. Its function is to flex your knee, extend your thigh at your hip and rotate your lower leg from side-to-side when your knee is bent.
• Semimembranosus. This muscle is on the innermost side of the back of your thigh. It flexes your knee joint, extends your thigh at your hip, and rotates your hip and lower leg.
• Semitendinosus. This muscle is between your semimembranosus and biceps femoris. Its function is the same as your semimembranosus.

What are your hamstrings made of?

Your hamstring muscles contain thousands of long, elastic muscle fibers. These fibers help your leg muscles contract, or tighten. So, your hamstrings might look striated (striped) if you could see them under your skin.

What conditions and disorders affect hamstring muscles?

Conditions that can affect your hamstring include muscle strains. These can occur as a result of overstretched muscle fibers. Hamstring strains can range from mild to severe. Hamstring strains include:

• Pulled hamstring. 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.
• Partial tear. One or more of your hamstring muscles is partially torn. Pain and swelling may prevent you from using your leg.
• Complete tear. 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.

What are the symptoms of hamstring injuries?

Hamstring muscle injuries may cause:

• An abnormal lump or indentation behind your thigh
• Bruising or skin discoloration on the back of your thigh
• 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 your thigh
• Sudden, sharp pain in the back of your thigh
• Swelling right after an injury

What are the risk factors for hamstring muscle injuries?

Hamstring 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 child or teen athlete who’s 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)
• Don’t perform proper warm-ups and stretches before activity

How can I keep my hamstrings healthy?

Take care of your hamstring muscles by:

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

When should I call my healthcare provider?

Contact your provider right away if you:

• Can’t move your leg and pain in your thigh that doesn’t go away
• Experience ongoing difficulty with walking
• Experience numbness in your lower back, hips or legs