The Hamstrings

September 21, 2014
The Hamstrings

The hamstrings group of muscles

The hamstrings include three separate muscles that work together: the semitendinosus, the semimembranous, and the biceps femoris.

Hamstring Muscles Location

Names and meaning of the names

  • Semitendinosus: semi means half and tendinosus means tightly stretched band (otherwise known as a tendon). This muscle is about half tendinous.
  • Semimembranosus: semi means half and membranosus means skin. The name of this muscle name refers to the sheath-like tendon of this muscle.
  • Biceps femoris: The name refers to the fact that this muscle has two (bi) portions.  It has a short head and a long head.

Attachments of muscles


  • Origin/proximal attachment: the ischial tuberosity, aka – the “sit bone.” (red circle on image)
  • Insertion/distal attachment: upper part of the tibia near the tibial tuberosity – an area known as the pes anserine. (blue circle on image)


  • Origin/proximal attachment: ischial tuberosity, aka – the “sit bone.” (red circle on image)
  • Insertion/distal attachment: the back of the inside top part of the tibia (posterior medial condyle of the tibia). (blue circle on image)

Biceps femoris:

  • Origin/proximal attachment:
    • Long head – ischial tuberosity, aka – the “sit bone”
    • Short head – bottom part of the femur next to a raised line called the linea aspera.
  • Insertion/distal attachment: outside of the head (top) of the fibula. (blue circle on image)

Hamstring Muscles Attachments

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Actions of the muscle

  • Knee flexion – all portions
  • Hip extension – all portions except the short head of the biceps femoris
  • Internal rotation of the knee joint (when flexed) – semitendinosus and semimembranosus
  • External rotation of the knee joint (when flexed) – biceps femoris both heads

You can read more about how the hamstrings contribute to movement at the knee joint (page 93, 1st  ed.) and the hip joint (pages 109-110, 1st ed.) in my book, Functional Anatomy of Yoga.

Poses that lengthen the hamstrings

prasarita padotanasana

Prasarita padottanasana lengthens the hamstrings even though the legs are wider than just a forward bend.

standing forward bend

Any type of standing forward bend will lengthen the hamstrings.

Poses that contract the hamstrings


Shalabasana uses the hamstrings to hyperextend the legs.

Injuries/issues with the hamstrings:

Hamstring strain: What is it?

When any one of the three hamstring muscles is stretched beyond its limit, a strain can occur. Hamstring strains tend to be either the result of sudden stopping and starting during a sport, sprinting for example, or extreme stretching as might occur in gymnastics, dance, or yoga. Hamstring strains from sudden stopping and starting tend to occur in the long head of the biceps femoris near its distal attachment, while stretch-related strains tend to occur near the proximal attachment of the hamstrings at the top of the thigh.

Risk factors that increase the chances of straining one or more of the hamstring muscles include:

  • Activities that require extreme stretching or a lot of sudden stopping and starting
  • Previous hamstring injury
  • Tight hamstrings
  • Inadequately warming up before exercise

Returning to sports or other activities that are demanding of the hamstrings before a hamstring injury has fully healed also increases the chances of a recurring hamstring injury.

There are three grades of hamstring strain. Grade 1 strains include milder strains that can be treated at home. However, grade 2 strains are more severe and include more loss of range of motion. Severe grade 3 strains may include avulsion, where some part of the muscle actually detaches from its connection to bone.


Generally, symptoms include a sudden sharp pain in the back of the thigh during exercise, when walking, or when bending over. It may be accompanied by a snapping feeling.

  • In a grade 1 strain, there is usually some tenderness or an indication of sudden pain in a point at the back of the thigh. Grade 1 may only cause slight pain or a sensation of tenderness in the thigh.
  • With a grade 2 strain, there might be a sudden sharp pain at the back of the thigh. There may be some bruising and/or swelling. There will likely also be some loss of range of motion.
  • In a grade 3 strain, there will likely be a sudden sharp pain at the back of the thigh, which is usually accompanied by swelling, bruising, and difficulty putting weight on the injured leg.


Treatment can range from home treatment to surgery depending on the severity of the hamstring strain, but in any case, you should consult a physician for recommendations on treatment.

Mild strains can be treated at home, but if there is severe pain and/or an inability to bear weight on the injured leg, an X-ray will be needed to look for an avulsion and an ultrasound or MRI will be needed to show severe muscle tears.

For more severe (grade 2 or 3) strains, your healthcare provider may recommend physical therapy exercises to help regain strength and mobility of the hamstrings.

For the most severe strains (grade 3), surgery may be required.

Hamstring tendonitis

Hamstring tendonitis is most commonly caused by over-use of the hamstring muscles.

Depending on the activity that has been repeated enough to cause the tendonitis, soreness, tenderness, and/or inflammation, may be felt either toward the proximal end of the hamstrings at the ischial tuberosity or toward the distal end of the hamstrings at the back of the knee.  You might be familiar with this sensation as sit bone pain.

Treatment generally includes rest, ice, and anti-inflammatory medications initially. It then can include bodywork, stretching, and strengthening exercises to restore strength and range of motion to the muscles. See a physician in order to determine the best course of treatment for your case.

Similar risk factors to those for a strain can contribute to hamstring tendonitis including:

  • Tight hamstrings
  • Inadequately warming up before exercise
  • Muscle weakness or imbalance between quadriceps and hamstring strength
  • Insufficiently healed previous hamstring injury

Trigger points

Keep in mind that trigger points can create pain at or near the sit bone. For more information on those trigger points, check out these two very popular articles here and here which also show images of trigger points that refer into the hamstrings.