AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

This article focuses on injuries to the hamstring muscles. The word "hamstrings" was derived from the fact that it is these muscles by which a butcher would hang a slaughtered pig.

The hamstrings are a group of muscles (ie, semimembranosus, semitendinosus, biceps femoris) located on the back of the upper leg.^{1, 2} The hamstrings are a common source of injury and chronic pain in athletes. Injuries to the hamstring muscles primarily occur proximally and laterally, and they usually involve the biceps femoris. The severity of injury to the hamstring muscles is classified according to the following grades:

• Grade 1 is a mild strain, with few muscle fibers being torn.
• Grade 2 is a moderate strain, with a definite loss in strength.
• Grade 3 is a complete tear of the hamstrings.

Hamstring injuries almost always occur at the proximal myotendinous junction. In the biceps femoris, this junction extends over most of its entire length. Injury usually does not occur within the tendon itself unless there is preexisting pathology.

Bony avulsion at the ischial origin may occur as well, but this is usually associated with sudden, large-force, hip-flexion injuries.³ Avulsions are commonly seen in individuals who have been involved in waterskiing accidents in which the knee is extended and the hip is suddenly flexed as the skier falls forward.⁴

One study involving 47 football players with hamstring injuries reported an average of 14 days of convalescence before return to play.

For excellent patient education resources, visit eMedicine's Sports Injury Center, Sprains and Strains Center, and Foot, Ankle, Knee, and Hip Center. Also, see eMedicine's patient education articles Muscle Strain and Ruptured Tendon.

Frequency

United States

As a percentage of lower-extremity injuries, hamstring injuries peak at 33% in persons aged 16-25 years, and they most often occur in sports in which the hamstrings can be stretched eccentrically at high speed.^{5, 6, 7, 8, 9, 10} Prime examples of such sporting activities include sprinting, track and field, and other running contact sports, such as football and soccer. Recreational sports such as waterskiing, in which the knee is fully extended during injury, are also common causes of hamstring injuries.⁴

International

An Australian study involving 1614 individuals with hamstring injuries revealed that such injuries compose 54% of the injuries in rugby, 10% of the injuries in soccer, 14% of the injuries in track, and less than 2% of the injuries in tennis, squash, ballet, and gymnastics.

Functional Anatomy

The hamstrings are composed of 3 muscles, as follows:

• Biceps femoris muscle (long head and short head)
• Semimembranosus muscle
• Semitendinosus muscle

Origins and insertions

All of the muscles of the hamstrings originate on the ischial tuberosity. The second head of the biceps femoris (ie, short head) originates medial to the linea aspera on the distal posterior femur.

The short head of the biceps femoris crosses only one joint to insert with the long head of the biceps femoris onto the fibular head and lateral tibial condyle.

The other hamstring muscles cross 2 joints to reach their insertions. The semitendinosus muscle forms the pes anserinus with the sartorius and gracilis tendons to insert on the medial tibial metaphysis. The semimembranosus muscle interweaves with the fibers of the semitendinosus to eventually insert onto the posteromedial tibial condyle.

Innervations

The short head of the biceps femoris muscle is also unique in that it is innervated by the peroneal portion of the sciatic nerve, whereas the long head of the biceps femoris, semimembranosus, and semitendinosus are innervated by the tibial portion of the sciatic nerve.

Sport-Specific Biomechanics

In track and field events in which the hamstring is eccentrically contracted, the risk of a hamstring injury can be high. Contact sports such as football can result in contusions of the hamstring muscle. The contusion is superficial when the muscle is contracted on impact, and it is deep when the muscle is relaxed on impact. Waterskiing accidents have an association with proximal, bony avulsions because the individual's knee is extended when the hip undergoes a violent, forceful flexion as he/she falls forward.

Related Medscape topics:
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Resource Center Trauma
Specialty Site Orthopaedics

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• The onset of pain and/or weakness is usually sudden and may occur during an explosive movement, such as sprinting.
• Patients may report hearing an audible pop at the time of injury.
• Onset of posterior thigh pain is often near the beginning or near the end of the sport activity. This is consistent with the belief that fatigue and lack of warm-up are factors that may lead to muscle injury.
• Patients may only have a sense of apprehension due to a feeling of inadequate leg control as a result of the injury.
• Patients may report pain with sitting or while walking uphill or ascending stairs.
• Swelling and ecchymosis may accompany more severe injuries.

Physical

• Physical findings are absent in many hamstring injuries.
• The patient often has pain with active knee flexion against resistance. The procedure is performed with the hip in a neutral position and the knee in an extended starting position.
• • With the patient in a prone position and the affected extremity's knee flexed at 90º, palpate from the ischial muscle origins to their insertions. This minimizes patient pain, which can limit detecting muscle defects.
  • Next, with the patient in the supine position and the hips flexed to 90º, the maximum tolerable active and passive knee extension angle should be noted and compared to the contralateral leg. This allows the physician to assess the severity of the injury and to monitor future rehabilitation progress.
• In severe cases, swelling and ecchymosis may be present.
• With a complete hamstring rupture, the muscle may contract into a ball, with an accompanying strength deficit.

Causes

• The major predisposing factors are lack of warm-up, poor flexibility, fatigue, and a hamstring-to-quadriceps ratio less than 50%.
• A previous hamstring injury is the most recognized risk factor for injury.
• Poor running style, especially overstriding, predisposes some runners to hamstring injuries. Overstriding stretches the hamstring and places it in a position of active insufficiency.
• Dyssynergia secondary to dual innervation of the hamstring muscles may also be a factor that contributes to hamstring injuries.
• Rapid growth seen during adolescence sometimes leads to tight hip flexors with a resultant anterior hip tilt. This can cause a natural predisposition to hamstring injuries for this age group.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to Be Considered

Apophysitis
Chronic hamstring syndrome
Ischial bony avulsion

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Laboratory studies are typically not needed to make the diagnosis of hamstring injury. Most often, a diagnosis can be made with the history and physical examination alone.

Related Medscape topic:
Resource Centers Pathology & Lab Medicine

Imaging Studies

• In most cases, imaging studies have no role in the workup of hamstring injuries.
• • Radiographs of the pelvis can be negative even though the patient may have a bony avulsion. However, radiographs may reveal calcifications that may be present in patients with chronic hamstring pain.
  • Ultrasound or magnetic resonance imaging (MRI) studies 2-3 days postinjury may be recommended to rule out total muscular rupture or an intramuscular hematoma if significant weakness is still present.
  • An MRI is often ordered to help clinicians prepare for possible surgery if radiographs reveal a gross deformity.

Procedures

• Past treatment options for acute hamstring injuries included intramuscular corticosteroids; however, given the evidence of delayed healing in acute muscle injury as well as muscle atrophy, this treatment could have detrimental effects over the long term.

  In a retrospective study of the use of intramuscular corticosteroid injection for hamstring injuries in professional football players, Levine et al found that players with a partial hamstring tear had no ill effects of the corticosteroid injection in terms of functional outcome¹⁰; however, the follow-up time frame was not clearly defined. Although this study does not address the issue of the physiologic effects of corticosteroids in muscle injury, it does offer some initial clinical outcomes for this procedure in athletes.¹⁰

Related eMedicine topics:
Corticosteroid Injections of Joints and Soft Tissues
Therapeutic Injections for Pain Management

Related Medscape topics:
Resource Center Pain Management: Advanced Approaches to Chronic Pain Management
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TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Acute Phase

Rehabilitation Program

Physical Therapy

Treatment of hamstring injuries varies according to the severity of the injury. Patients with minor strains may progress quickly to strengthening exercises, whereas those with full-thickness ruptures require surgery. Up to 1 week after a minor injury, the focus of therapy is to limit pain, inflammation, and swelling. Rest, ice, compression, and elevation (RICE) are recommended. Elastic thigh bandages can be useful for compression. Icing for 20 minutes, 4 times per day, provides pain relief.

Most patients may begin active range of motion (AROM) exercises within their pain tolerance after 1-2 days. Individuals with more serious injuries benefit from immobilization in knee extension for 1-5 days to prevent contracture formation and further damage. Crutches enable ambulation while resting the injured leg.

After several days, most patients may begin pain-free submaximal isometrics, pool therapies, and upper-body exercises. Isometric exercises are performed at various knee angles in increments of 20°. Patients hold the contraction for 5-15 seconds, and perform 3 sets at each angle.

Related eMedicine topic:
Therapeutic Exercise

Medical Issues/Complications

If patients return to their usual activities too soon, delayed healing or reinjury may result. In more serious injuries, compartment syndrome can result from an extending hematoma. The most common symptom of compartment syndrome is increasing pain.

Surgical Intervention

Surgery is rarely performed for large hematomas; on the other hand, it is performed in more than 50% of cases of muscle belly tears, with consideration given to the patient's activity demands. However, surgery is generally indicated for bony avulsions only.

Consultations

In cases of severe hamstring injuries, consultation with a sports medicine specialist or an orthopedic surgeon may be indicated. Physiatrists may be consulted to oversee rehabilitative therapies and to help prevent further injuries.

Related eMedicine topic:
Adult Physiatric History and Examination

Recovery Phase

Rehabilitation Program

Physical Therapy

Generally, treatment 1-6 weeks postinjury focuses on patient strengthening, improving range of motion (ROM), and flexibility.

Passive static stretching may begin at this stage. Moist heat may be used to warm up the muscle tissues before stretching and exercising. Electrical stimulation may be used in conjunction with ice for added pain relief.

Being pain free throughout the entire ROM is not required before strengthening exercises may be initiated. The patient may exercise, preferably with a therapist, to strengthen the muscle within the available pain-free ROM.

Next, the patient begins isotonic exercises with resistance, increasing the program gradually as tolerated. As healing continues, high-speed, low-resistance isokinetic exercises are started. Resistance is increased gradually, while exercise speed is decreased. Over time, the patient progresses from concentric to eccentric strengthening exercises. Before the athlete returns to play, sports-specific training maximizes recovery and minimizes the chances for additional injury.

Related eMedicine topic:
Therapeutic Exercise

Medical Issues/Complications

Reinjury and delayed healing result if the therapy is too aggressive or if activity limitations are not followed.

Maintenance Phase

Rehabilitation Program

Physical Therapy

From 1 month postinjury onward, the patient continues stretching and strengthening exercises to maintain flexibility and an adequate hamstring-to-quadriceps strength ratio.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Although some inflammation may theoretically be desirable to facilitate clearing of necrotic tissue and to initiate healing, nonsteroidal anti-inflammatory drugs (NSAIDs) are usually started right away. However, NSAIDs are ideally used for only 3-7 days, given the evidence that their use may delay complete healing.

Acetaminophen or a narcotic may be administered in addition to an NSAID for most continuing pain. However, narcotics (eg, Vicodin) are usually reserved for those with serious injuries and extreme pain.

Some animal model studies show some evidence that anabolic steroids may aid in the healing of injured muscles. Animals that have been treated with anabolic steroids are able to generate greater forces through injured muscles than those that have not been treated with these agents. However, there is not enough evidence to recommend the use of anabolic steroids to promote faster healing.

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Toxicity, Acetaminophen
Toxicity, Narcotics
Toxicity, Nonsteroidal Anti-inflammatory Agents

Drug Category: Nonsteroidal Anti-inflammatory Agents

NSAIDs have analgesic and antipyretic activities. The mechanism of action of these agents is not known, but NSAIDs may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation and various cell membrane functions. Treatment of pain tends to be patient specific.

Drug Category: Analgesics

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or who have sustained injuries.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Return to Play

A common threshold for return to play is when the strength of the injured hamstring has at least 90% of the strength of the unaffected hamstring and when the patient has full ROM. At least a 50-60% hamstring-to-quadriceps ratio is desired before allowing the athlete to return to play.

Strength testing is performed using isokinetic exercise equipment. In addition, it is also important to ensure the return of normal flexibility and endurance before the patient returns to play; reinjury is most often due to lack of both.

Therapy that incorporates sports-specific activities can help minimize the risk of reinjury.

Complications

Returning to play too early is a common factor leading to chronic hamstring pain and injury. Reinjury rates as high as 77% may be related to areas of calcification and inflammation in the hamstring after injury. Scar formation may impinge the sciatic nerve, resulting in hamstring syndrome. Surgery has rarely been used to break up painful scar tissue.

Related eMedicine topics:
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Laser Revision of Scars

Related Medscape topic:
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Prevention

The implementation of proper warm-up and maintenance of flexibility and adequate strength are needed to prevent future injuries. The patient should be aware that as fatigue sets in, the risk of injury increases. With improved form and by emphasizing knee flexion during activities, the risk of further injuries is minimized.^{2, 7, 8, 11, 12, 13}

Prognosis

With minor activity limitations and proper rehabilitation, the prognosis is good for hamstring strains and even partial tears. Complete tears also heal but require a significantly longer and more intensive rehabilitation program.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• An individual's premature return to play may result in recurrent injuries and chronic debilitating hamstring pain. Monitor individuals for increasing pain, which may indicate an expanding hematoma, potential compartment syndrome, and a need for further workup.

Related Medscape topics:
Resource Center Medical Malpractice and Legal Issues
Resource Center Pain Management: Advanced Approaches to Chronic Pain Management
Resource Center Pain Management: Pharmacologic Approaches

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Davis KW. Imaging of the hamstrings. Semin Musculoskelet Radiol. Mar 2008;12(1):28-41. [Medline].
2. Reid DC. Soft tissue injuries of the thigh. Sports Injury Assessment and Rehabilitation. Philadelphia, Pa: Churchill Livingstone; 1992:551-71.
3. Sarimo J, Lempainen L, Mattila K, Orava S. Complete proximal hamstring avulsions: a series of 41 patients with operative treatment. Am J Sports Med. Jun 2008;36(6):1110-5. [Medline].
4. Sallay PI, Friedman RL, Coogan PG, Garrett WE. Hamstring muscle injuries among water skiers. Functional outcome and prevention. Am J Sports Med. Mar-Apr 1996;24(2):130-6. [Medline].
5. Askling CM, Tengvar M, Saartok T, Thorstensson A. Proximal hamstring strains of stretching type in different sports: injury situations, clinical and magnetic resonance imaging characteristics, and return to sport. Am J Sports Med. Apr 30 2008;epub ahead of print. [Medline].
6. Croisier JL, Ganteaume S, Binet J, Genty M, Ferret JM. Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study. Am J Sports Med. Apr 30 2008;epub ahead of print. [Medline].
7. Clark RA. Hamstring injuries: risk assessment and injury prevention. Ann Acad Med Singapore. Apr 2008;37(4):341-6. [Medline]. [Full Text].
8. Clanton TO, Coupe KJ. Hamstring strains in athletes: diagnosis and treatment. J Am Acad Orthop Surg. Jul-Aug 1998;6(4):237-48. [Medline].
9. Hoskins W, Pollard H. The management of hamstring injury-- part 1: issues in diagnosis. Man Ther. May 2005;10(2):96-107. [Medline].
10. Levine WN, Bergfeld JA, Tessendorf W, Moorman CT 3rd. Intramuscular corticosteroid injection for hamstring injuries. A 13-year experience in the National Football League. Am J Sports Med. May-Jun 2000;28(3):297-300. [Medline].
11. Kujala UM, Orava S, Järvinen M. Hamstring injuries. Current trends in treatment and prevention. Sports Med. Jun 1997;23(6):397-404. [Medline].
12. Unger CL, Unger DA. Preventing and rehabilitating hamstring injuries. Athl Ther Today. May 1997;44-9.
13. Worrell TW. Factors associated with hamstring injuries. An approach to treatment and preventative measures. Sports Med. May 1994;17(5):338-45. [Medline].

Article Last Updated: Jun 16, 2008