The hamstrings are a group of muscles located on the back of the thigh. They extend from just below the buttocks to just past the knees. The hamstrings group is subdivided into medial and lateral parts. The medial hamstrings (the semitendinosis and semimembranosis) attach to the inside part of the back of the knee and the lateral hamstrings (biceps femoris) attach to the outside part of the back of the knee. The functions of the hamstrings group are to extend the hips and to flex the knees. Because these muscles cross two joints and are involved in explosive actions like running and jumping, they are vulnerable to injury. A torn medial hamstring has standard symptoms.
Pain
Hamstring injuries are one of the most common injuries associated with sports participation, according to a 2008 article published in the "Annals of the Academy of Medicine, Singapore." The injury usually occurs during running, especially sprinting. During the "swing phase" of the gait the hip is flexing and the knee is extending rapidly as the opposite limb is in contact with the ground. This rapid stretch of the hamstrings can surpass the elastic limits of the muscle resulting in a tear (strain). When the medial hamstrings are involved, there will be an intense cramping pain on the inside portion of the back of the thigh. The pain will prevent continued running and may even thwart weight-bearing on the painful leg. It is common to see an athlete drop to the track or turf clutching the back of the thigh in pain at the onset of a hamstring injury.
Stiffness
Immediately following a medial hamstring tear, the muscles may be so tight and painful that it is not possible to even straighten the leg. Days, or even weeks later, tightness in the damaged muscle may continue to make difficult such tasks as bending to pick something up from the floor or tying your shoes. This stiffness may persist for some time. In 2006, the "British Journal of Sports Medicine" published a study that tracked the recovery of hamstring flexibility following injuries to sprinters and dancers. Though there was a gradual improvement in flexibility, there was still not a 100 percent recovery of flexibility even at the end of the six-week study.
Bruising
Muscle tissue is has many blood vessels, so when you tear a muscle it will tend to bleed. Depending on the location and severity of the tear, it may take a day or more for the blood to migrate close enough to the skin to appear as a bruise. Sometimes gravity and body position factors cause the bruising to appear in an area somewhat distant from the point of injury. Milder hamstring injuries may not result in significant bruising.
Weakness
Naturally, a muscle that is torn will not be capable of contracting as effectively as a non-injured muscle. There will be some weakness with activities such as squatting, climbing stairs and lifting objects from a low position. This weakness is due to a combination of the direct effects of the tear and by reduced efforts due to pain when the injured muscle contracts. The return of strength in the injured hamstring roughly parallels the return of flexibility in terms of timing.
References
- "Annals of the Academy of Medicine, Singapore;" Hamstring Injuries: Risk Assessment and Injury Prevention; RA Clark; Apr. 2008
- "British Journal of Sports Medicine;" Type of Acute Hamstring Strain Affects Flexibility, Strength, and Time to Return to Pre-Injury Level; C Askling, T Saartok, and A Thorstensson; Jan. 2006
