A hamstring strain is a common leg injury involving a tear in one or more of the hamstring muscles. A hamstring strain can range from mild to very severe involving a complete tear of the hamstring muscle.

Hamstring muscle group comprises of 3 muscles: semimembranosus and semitendinosus medially (inner side of thigh) and biceps femoris – short and long heads laterally (outer side of thigh).


The reasons for hamstring strain or injury can be categorized into primary or secondary.


Poor coordination and firing time of front and back muscles of the thigh. The simultaneous eccentric and concentric contraction in the hamstring muscles during the switch between late leg recovery and initial leg approach in the swing phase of sprinting.


  • Poor running mechanics – If runners over-striding or have poor pelvic control, it will puts the hamstrings in a vulnerable position at ground contact.
  • Improper warm – up – Proper warm-up is needed to prepare the hamstring muscles. Passive stretching is only one segment of warm-up.
  • Inappropriate overloaded training – Hamstrings are primarily composed of fast twitch Type II fibers that tires up relatively early. Hence High speed work should be done early during workout.
  • Fatigue – if proper recovery time is not given, it may strain the hamstring.
  • Lower back pathology – Lower back anomalies causes’ nerve dysfunction and subsequent muscle weakness which can predispose hamstring to injury.
  • Playing surfaces – A wet slippery surface puts more strain on the hamstring.


Mild hamstring strains are more like low grade ache or tightness in hamstring region (back of thigh). Severe hamstring strains can be quite devastating ranging from excruciating pain to making it difficult to walk or even stand.

Other symptoms may include

  • Severe pain during exercise, along with a snapping or popping feeling.
  • Pain may range from lower buttock region to hamstring insertion.
  • Pain with bending and straightening of leg or while bending over like touching the toes.
  • Tenderness over the hamstring belly.
  • Bruising.


A well trained physiotherapist will observe/ examine signs of pain on hamstring contraction against resistance, compromised hamstring flexibility, tenderness or a palpable lump or gap within the hamstring muscle bulk. Pulled hamstrings are graded into 3 types depending on severity.

Ultrasound scan and MRI can be used to identify the location and extent of hamstring tear.

Grade 1 Hamstring Strain

With a grade 1 hamstring strain, there is tightness in back of the thigh but the patient will be able to walk normally. Patient is aware of some hamstring discomfort and will be unable to run at full speed. There may be mild swelling and spasm. Bend your knee against resistance is unlikely to reproduce much pain.

Grade 2 Hamstring Strain

With a grade 2 hamstring strain, walking pattern will be affected and patient most likely be limping. Sudden twinges of hamstring pain during activity will be present. Noticeable hamstring muscle swelling and tenderness will be present. Knee bend against resistance will be painful.

Grade 3 Hamstring Strain

grade 3 hamstring strain is a severe injury involving a tear to half or all of the hamstring muscle. Patient may need crutches to walk and will feel severe pain and weakness in the muscle. Swelling will be noticeable immediately and bruising usually appears within 24 hours.