Hamstring pulls are one of the most common types of muscle strains, especially among those whose preferred form of exercise is running. Whether it's hitting the pavement for a marathon training session or taking an easy jog on the treadmill just to keep in shape, hamstring pulls can result in minor strains or more serious pulls of the muscles along the back of the thighs.
The three muscles that run along the back of the legs from below the knee to just above the hip constitute the hamstrings. Flexing the knee and extending the thigh--motions involved in running--are dependent on the hamstrings.
Minor hamstring strains can be caused by overworking or overstretching the group of muscles at the back of the thigh. According to the Mayo Clinic Family Health Book, pain or weakness along the hamstrings may indicate a pulled muscle. A sharp, localized pain is often followed by tenderness and/or swelling when a hamstring strain occurs. Swelling usually develops soon after the injury is sustained. The next day, stiffness or tenderness in the hamstrings may persist. Hamstring spasms and the inability to use the hamstring to either flex the knee or extend the thigh are other symptoms of a pulled muscle. Hamstring strains also may prevent you from putting weight on the leg.
A more serious injury, often following sudden stress or a direct blow to the hamstring, results when fibers within the muscle actually tear. A tear in the hamstring causes the muscle to contract and bleed internally. Hamstrings also may rupture either entirely or partially. The damage levels of hamstring pulls are classified from grade 1 to grade 3. According to the Johns Hopkins Family Health Book, grade 1 refers to a mild stretch, grade 2 refers to a partial tear, and grade 3 indicates a complete tear. In more serious injuries, those diagnosed as grade 2 or 3, a pop may be heard as the muscle ruptures, or a snapping sensation may be felt. Bruising on the back of the thigh can follow if blood vessels are broken. Unlike swelling, bruising may not occur until days or weeks following the initial pain. The bruising also may develop in areas other than the hamstrings as the blood from the damaged tissues spreads out from the muscle before reaching just below the skin, sometimes resulting in a rather large black-and-blue area.
Hamstring pulls can be confused with sciatica, or pain radiating from the sciatic nerve, which runs from the back of each leg up to the buttocks and up the spinal cord. To distinguish between these two types of injuries, two simple exercises can be performed. While on your back, raise one leg with your knee straight. If pain results, a hamstring injury is likely. If not, recruit a friend to bend your foot toward your knee. Pain from this exercise usually indicates sciatica. A hamstring pull is often felt more in the center of the back of the leg, while sciatica is commonly felt on the outer area of the thigh.
See a Doctor
A visit to the doctor is in order if significant pain or swelling is felt in the leg, or if you cannot use the muscles normally despite the pain.