Hamstring Strains
Hamstring strains are a very common injury across many sports, but are even more common in the running community. The hamstring is comprised of three muscles: the semitendinosis, semimembranosis, and the biceps femoris. The biceps femoris is further subdivided into the long and short heads, and is the most commonly injured hamstring muscle. 2, 6, 7 The hamstring muscles originate at the ischium and insert at both the tibia and fibula. The semitendinosis and the semimembranosis are located medially and insert on the tibia below the knee joint. The biceps femoris runs laterally and inserts on the head of the fibula and the tibia.
The action of the hamstrings is to extend the hip and flex the knee.6 When running, muscle fibers contract and relax in response to neuron activity. Muscle contractions shorten the muscle, which causes movement. The hamstrings are responsible for pushing-off from the ground to propel the runner forward during the terminal swing phase.1,6
A muscle strain occurs when a muscle is stretched beyond its typical capacity. This can occur when an athlete over-trains causing fatigue, fails to properly warm-up prior to activity, or when they progress too quickly into activity. Other risk factors include weakness of one hamstring as compared to the contralateral side, or weakness of the hamstring as compared to the ipsilateral quadriceps.3
An acute muscle strain happens frequently in sprinting events, where a sprinter will stop running mid-race. The pain can vary from a sharp stabbing pain, to a dull, achy pain. Hamstring strains typically occur in the mid-muscle belly of the biceps femoris. Depending on the severity of the strain, there may be a visible deformity in the muscle belly, bruising, or swelling. Strains are graded on a scale of 1–3 with a Grade 3 strain being the most severe.4
Grade 1: A mild strain where a small number of muscle fibers are torn with no loss in strength.
Grade 2: Moderate strain with increased fiber tearing and some impairment in strength.
Grade 3: More severe strain with complete disruption in the muscle and loss of strength.
Hamstring strains respond well to the RICE acronym: rest, ice, compression, and elevation. Anti-inflammatories, such as Ibuprofen and Advil can be helpful to reduce inflammation. MRI scan can identify the location and extent of a tear, but it is not routinely necessary. Physical therapy can restore the muscle function and range of motion. Low intensity isometric exercises should progress into eccentric hamstring work with resistance bands, followed by higher intensity, sport-specific drills.6
A return to running protocol can begin when the athlete is pain free, has full range of motion, and full strength. More severe grade 3 injuries can take longer to heal and these patients may benefit from injection treatment with either platelet rich plasma or corticosteroids.
Return to play time varies based on the injury and level of competitive play. For an athlete to return to play, flexibility and strength should be similar to that of the contralateral limb, and functional skills such as running and jumping should be performed without pain.
In cases where there is a complete disruption of the muscle with retraction, there can be a significant loss in function. These injuries should be evaluated by a medical provider. Furthermore, skeletally immature athletes can avulse their ischium from forceful contraction of the hamstring, causing the the bone to which the tendon attached to become injured. These are more serious injuries and should be evaluated by a medical provider.
Proper warm-up is important to maintain hamstring health. Additionally, ensuring adequate hydration status is important for blood flow to the muscles.
Hamstring strains have a high rate of recurrence, with at least one third of hamstring strains reoccurring within two-weeks of return to play.5 Athletes and medical staff should take into consideration the recurrence rate when developing injury prevention strategies and returning their athletes to sport.
References
1. Heiderscheit B.C., Sherry M.A., Silder A., Chumanov E.S., Thelen D.G. Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention. J Orthop Sports Phys Ther. 2010;40(2):67–81.
2. Heiderscheit B.C., Hoerth D.M., Chumanov E.S., Swanson S.C., Thelen B.J., Thelen D.G. Identifying the time of occurrence of a hamstring strain injury during treadmill running: a case study. Clin Biomech (Bristol, Avon) 2005;20(10):1072–1078.
3. Heiser T.M., Weber J., Sullivan G., Clare P., Jacobs R.R. Prophylaxis and management of hamstring muscle injuries in intercollegiate football players. Am J Sports Med. 1984;12(5):368–370.
4. Järvinen T.A., Kääriäinen M., Järvinen M., Kalimo H. Muscle strain injuries. Curr Opin Rheumatol. 2000;12(2):155–161.
5. Orchard J., Best T.M. The management of muscle strain injuries: an early return versus the risk of recurrence. Clin J Sport Med. 2002;12(1):3–5.
6. Ramos, G. A., Arliani, G. G., Astur, D. C., Pochini, A. de C., Ejnisman, B., & Cohen, M. (2017). Rehabilitation of hamstring muscle injuries: a literature review. Revista Brasileira de Ortopedia, 52(1), 11–16.
7. Schache A.G., Wrigley T.V., Baker R., Pandy M.G. Biomechanical response to hamstring muscle strain injury. Gait Posture. 2009;29(2):332–338.
