Progression of a Hamstring Pull
This can be classified into 3 grades of hamstring strain severity:
Minor - Grade 1 Hamstring Pull involve stretching of your hamstring muscles which result in slightly pulled or excessively stretched muscles, or very small tears in your muscles. You will generally feel some specific point pain, tightness or mild cramping in your hamstring which will be a little uncomfortable, but will involve no swelling or no major loss of strength. These may diminish with activity, but will return with a vengeance afterwards.
Moderate - Grade 2 Hamstring Pull are more painful and involve a partial tearing of the hamstring fibers in your muscles, tendons, or at the tendon attachment to your bone. You will generally experience some pain that radiates down your leg during activity, while bending your knee against resistance, or when you touch your hamstring. Swelling, stiffness, decreased strength and range of motion (may not be able to straighten knee) will be apparent and can also cause you to limp. You may also experience some bruising (ecchymosis) due to bleeding within the injured muscle.
Severe - Grade 3 Hamstring Pull involve a complete tear (rupture) of your hamstring muscle fibers where your muscle belly attaches to your tendon or where your muscle belly rips in 2 separate pieces. It is very painful and rarer than the other strains. You will tend to experience a burning or stabbing pain, a lot of swelling and minimal strength, which may prevent you from walking without assistance or make it difficult for you to move your leg. Discoloration and widespread bruising in the injured area as a result of bleeding in the muscle tissue can also happen. You may also notice a break in your normal muscle outline that makes a gap under your skin where the muscle has come apart. This can be seen or felt with your hands and looks like a knotting of the muscle that produces a bulge.
The majority of hamstring strains are grade 1 or 2 strains that involve partial muscle or tendon tears that occur near the musculotendinous junction, where your hamstring tendon and muscle meet.
Should you seek medical attention?
This is up to your discretion; however any continued discomfort in your hamstring should be investigated. If you continue to experience the hamstring injury symptoms and have tried the suggested conservative treatments for 2-3 weeks, it is recommended that you seek professional medical attention. It is recommended you seek immediate attention if you:
hear a "loud pop" in your muscle when injured
have immediate severe pain, swelling or discoloration in your hamstrings
experience severe weakness in your leg (compared to other leg) and have difficulty walking
have a temperature over 100.4¼ F (38¼ C)
notice blue toe nails, numbness or coldness below your injury