How Do You Judge the Severity of a Pulled or Strained Hamstring?

To assess your level of hamstring injury, a doctor will typically discuss your symptoms, your overall health, and how the injury happened. The doctor will check for tenderness, bruising, pain, and/or weakness in your hamstrings, specifically when you are contracting the muscle group and against resistance.

Your pulled hamstring will be graded according to the following:

Grade 1
You have overstretching the hamstring muscles, causing micro-tearing of the fibers. This will typically cause on or more of the following:

tightness in the back of the upper leg
ability to walk normally, but aware of discomfort and perhaps a minor limp
minimal swelling
straightening the knee against resistance will not cause too much pain, but will cause some

Grade 2
You have experienced partial tearing of the muscle fibers. You may experience:

affected walk, including potential for a limp
twinges of pain during activity
visible swelling
applying pressure increases hamstring pain
pain when flexing the knee, especially against resistance
inability to lock the knee (straight leg)
inability to bend the knee fully

Grade 3
You have experienced full tearing of the hamstring muscle fibers (rupture). You may experience:

severely affected walk, including potential to need crutches
severe pain, especially when bending the knee
visible and immediate swelling
contraction will cause pain and potential bulging/spasm of the muscle

Chronic Injury
In addition to the three grades of injury, you may also have a chronic hamstring pull. A chronic injury is one that is persistent and recurring and is identified by the following symptoms:

You experience stiffness and soreness for over one month
Your hamstring constantly feels a bit weak, or "stuck" and despite recovery efforts it is still not functioning at full strength

If you have previously had a hamstring strain and did not allow the muscles to heal fully before returning to your normal activities and exercise, your chance of developing a chronic strain are orders of magnitude greater. Often, in such instances, you are susceptible to muscle imbalances between your leg muscles (for example, between the quads and hamstrings) that will cause continued stress that sets up the chance for reinjury.

Note: Seek medical attention if you have difficulty walking, or the pain is significant or unbearable.