Proximal hamstring injuries can present as chronic tendinosis, acute strain, partial tendinous avulsions, or complete 3-tendon rupture. Nonoperative management for chronic insertional tendinosis and low-grade tears includes activity modification, anti-inflammatories, and physical therapy. Platelet-rich plasma injections, corticosteroid injections, dry needling, and shock wave therapy are newer therapies that also may provide benefit. Surgical indications include complete, proximal avulsions; partial avulsions with least 2 tendons injured with more than 2 cm of retraction in young, active patients; and partial avulsion injuries or chronic tendinosis that have failed nonoperative management. Surgical management entails open primary repair, endoscopic primary repair, or augmentation/reconstruction.
Key points
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Proximal hamstring injuries can present as chronic tendinosis, acute strain, partial tendinous avulsions, or complete 3-tendon rupture. The mechanism of injury results from chronic repetitive or acute eccentric loading during hip flexion and knee extension.
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Patients often present with posterior hip pain located at the buttock/ischial tuberosity, posterior thigh ecchymosis, or a mass of retracted muscle if acutely injured, a stiff-leg gait, and exacerbation of pain with hip flexion and knee extension.
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Nonoperative management for chronic insertional tendinosis and low-grade, partial tears includes activity modification, oral anti-inflammatories, and physical therapy. Platelet-rich plasma injections, corticosteroid injections, dry needling, and shock wave therapy are newer treatment modalities being studied that may provide additional benefit.
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Surgical indications include complete, proximal avulsions; partial avulsions with least 2 tendons injured with greater than 2 cm of retraction in young and active patients; and partial avulsion injuries that have failed nonoperative management.
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Surgical management entails open primary repair, endoscopic primary repair, or augmentation/reconstruction.
Introduction
Hamstring injuries are one of the most frequently occurring injuries in sports, accounting for 12% to 29% of all injuries in athletes. After an initial injury, athletes have increased rates of reinjury as high as 22% to 34%. Injuries can occur at any level of the musculotendinous unit. Proximal hamstring injuries represent 12% of all hamstring injuries, whereas most injuries occur more commonly at the musculotendinous junction. These injuries include a spectrum of disease from strain to complete rupture. Although proximal hamstring pathology has historically been recognized, proximal injuries were not reported on until 1988 when the first case series of complete proximal hamstring avulsions was published. The management of these injuries continues to evolve depending on the severity of injury and patient-specific factors.
Pertinent anatomy
There are 3 hamstring muscles: the semimembranosus, semitendinosus, and the long head of the biceps femoris. These muscles share a common origin at the ischial tuberosity; however, with 2 distinct footprints, as seen in Fig. 1 . The semimembranosus originates from the superolateral ischial tuberosity. The semitendinosus and long head of the biceps femoris form the conjoint tendon, which originates medial to the semimembranosus at the superomedial ischial tuberosity. The hamstring muscles cross both the hip and knee joint, inserting distally below the knee on the proximal tibia. The hamstring muscles are innervated by the tibial branch of the sciatic nerve and receive their arterial supply from the perforating branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of popliteal artery. Together the hamstring muscles extend the thigh, flex the knee, and internally rotate the tibia. They are active throughout the gait cycle, but primarily in terminal swing phase to slow knee extension. The hamstrings also help initiate hip extension and continue to function during early stance phase to assist with hip extension.
Risk factors for hamstring injury
Several risk factors for hamstring injuries have been proposed in the literature, including decreased flexibility, strength deficits, muscle fatigue, poor core stability, lack of proper warm-up, poor lumbar posture, and a prior hamstring injury. , Previous hamstring strain has been recognized as the strongest risk factor for recurrent strain among all the risk factors examined with an increased risk of recurrence by 2 to 6 times. In addition, a 2015 epidemiologic study investigating hamstring injury in 25 National Collegiate Athletic Association sports demonstrated a higher rate of hamstring injury in male athletes than female athletes, specifically for soccer, baseball/softball, and indoor track.
Injury classification
Hamstring injuries can occur at any level along the musculotendinous unit, but commonly occur at the myotendinous junction. Koulouris and Connell demonstrated that only 12% of hamstring muscle injuries were proximal ruptures and 9% were complete. Understanding the location, severity, and acuity of proximal hamstring injuries is important when considering management options. When evaluating the injury severity and appropriate management options, classification considerations include the following:
Grade
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First described by the American Medical Association subcommittee in 1966, the 3-grade system for acute muscle injuries can help classify hamstring injuries.
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Grade 1 (tendinosis): Muscle soreness with no appreciable muscle tearing, less than 5% loss of function/strength
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Grade 2 (partial): Partial damage to the musculotendinous unit, reduced strength, some residual function
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Grade 3 (complete): Complete tear across the whole cross-section of the musculotendinous unit or discontinuity of the tendon-bone unit, loss of function, may have a palpable gap or mass from retraction
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Location
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Insertional:
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Bony involvement
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Periosteal, bony, or apophyseal avulsion
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This is typically seen in younger patients that are skeletally immature. Referred to as a “hurdler’s fracture” or also commonly seen in water skiers.
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Tendinous avulsion
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Musculotendinous junction
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Midsubstance muscle injury
Acuity
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Acute: less than 6 weeks of symptoms
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There is no consensus on the definition of acute with studies ranging from less than 4 to 12 weeks
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Chronic: more than 6 weeks of symptoms
Mechanism
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Traumatic: Identifiable injury
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Atraumatic (attritional): No known injury or inciting event
Number of Tendon Involvement
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Hamstring injuries can involve 1, 2, or all 3 tendons. The most commonly injured tendons include the semitendinosus and biceps; the semimembranosus is the least commonly injured.
Specific Terms
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Tendinopathy: Umbrella term for any tendon condition
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The term proximal hamstring tendinopathy is used to describe an overuse injury that involves pain at the attachment of the hamstring tendons to the ischial tuberosity.
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Tendinosis: Noninflammatory degeneration of a tendon, often from strain injuries
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Tendinitis: Acute inflammation of the tendon due to small micro-tears
Broadly speaking, proximal hamstring pathology can be divided into 3 main categories: chronic insertional tendinopathy, partial-thickness hamstring tears, and full-thickness hamstring tears. Chronic insertional tendinopathy was first described as “hamstring syndrome” in 1988 and is common among long-distance runners and hurdlers.
Mechanism of injury
The mechanism of injury is typically a result of an eccentric load during hip flexion and knee extension that results in excessive hamstring tension. This may occur as an acute injury or in the setting of chronic overuse. High-risk activities include sprinting, water skiing, or other sporting activities that require rapid acceleration and deceleration.
Clinical presentation
Injuries can occur in both young athletes or middle to older-aged individuals who sustain sudden or repetitive hip flexion and knee extension. It is important to obtain a thorough history of the patient’s symptoms and baseline functional level. Patients with an acute proximal hamstring injury typically report a “popping” sensation with sudden severe pain about their ischium/buttock and startup pain with ambulation. They may recount a mechanism of injury with sudden concurrent hip flexion and knee extension such as a “split” type mechanism. They often present with ecchymosis in the posterior thigh and avoidance of painful simultaneous hip flexion and knee extension resulting in a stiff-leg gait pattern.
Chronic insertional tendinopathy is often more vague and difficult to diagnose. Chronic pathology is more commonly seen in endurance athletes, most notable when participating in running sports in which terminal hip flexion and knee extension elicits symptoms. Patients present with insidious onset of symptoms including an ill-defined pain at the ischial tuberosity with radiation distally down the muscle belly to the popliteal fossa. Pain with prolonged sitting is common. Functional pain exacerbated with acceleration activities is a more specific finding. Occasionally, sciatic nerve irritation can occur due to the close proximity of the nerve to the hamstrings resulting in posterior thigh pain and radiation down the leg.
Physical examination
The physical examination should consist of a comprehensive examination of the involved lower extremity, contralateral side, and lumbar spine. Observe the patient’s gait for a stiff-leg pattern and avoidance of hip and knee flexion. Inspection should include examining the posterior thigh for ecchymosis, swelling, a local mass of retracted muscle, or other evidence of trauma. Tenderness to palpation at the ischial tuberosity is common. Palpation over the mid-thigh can identify avulsed or retracted tendons. Hip range of motion and strength (flexion, extension, adduction, abduction, internal rotation, and external rotation) and knee range of motion (flexion, extension) should be evaluated. Patients with a proximal hamstring injury may guard with attempted hip flexion and exhibit weakness due to pain. A careful neurologic evaluation should be performed to assess for sciatic nerve irritation, including posterior thigh sensation and distal motor and sensory function of the tibial and peroneal nerves. Any neurologic deficits not limited to the sciatic nerve should warrant a further spine workup.
There have been a few studies evaluating the diagnostic accuracy of orthopedic special tests for hamstring injuries to determine their clinical utility. Suggested provocative tests are outlined in Table 1 with their corresponding sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios. These tests can be especially important in the setting of chronic pathology or partial injuries in which the presentation is more equivocal.
| Test | How to Perform | Positive | Data |
|---|---|---|---|
| Chronic proximal hamstring tendinopathy | |||
| Puraenen-Orava | Patient standing Actively stretch the hamstring muscles with the hip flexed at about 90°, the knee fully extended, and the foot on a solid support surface. | Exacerbation of patient’s symptoms | Sensitivity: 0.76 Specificity: 0.82 PPV: 0.81 NPV: 0.77 Positive likelihood ratio: 4.2 Negative likelihood ratio: 0.29 (Cacchio et al., 2012) |
| Bent knee stretch | Patient supine The hip and knee of the symptomatic leg are maximally flexed, and the examiner slowly straightens the knee while keeping the hip flexed. | Exacerbation of patient’s symptoms | Sensitivity: 0.84 Specificity: 0.87 PPV: 0.86 NPV: 0.85 Positive likelihood ratio: 6.5 Negative likelihood ratio: 0.18 (Cacchio et al., 2012) |
| Modified bent knee stretch | Patient supine The lower extremities are fully extended. The examiner grasps the heel of the symptomatic limb with one hand and places the other hand on the knee. The examiner then maximally flexes the hip and knee of the symptomatic leg and rapidly extends/straightens the knee. | Exacerbation of patient’s symptoms | Sensitivity: 0.89 Specificity: 0.91 PPV: 0.91 NPV: 0.89 Positive likelihood ratio: 10.2 Negative likelihood ratio: 0.12 (Cacchio et al., 2012) |
| Hamstring strain | |||
| Taking-off-the-shoe test | Patient standing The patient attempts to take off the shoe on the affected side with the help of his or her other shoe. While performing this maneuver, the affected leg hindfoot must press the longitudinal arch of the noninvolved foot. The affected leg during the maneuver is in approximately 90° of external rotation at the hip and 20° to 25° of flexion at the knee. | The feeling of a sharp pain over the injured biceps femoris | Sensitivity: 1.0 Specificity: 1.0 PPV: 1.0 NPV: 1.0 Positive likelihood ratio: 208.0 Negative likelihood ratio: 0.0 (Zeren and Oztekin, 2006) |
| Active range of motion test |
| Reproduction of patient’s pain with either test | Sensitivity: 0.55 Specificity: 1.0 PPV: 1.0 NPV: 0.70 Positive likelihood ratio: 154.6 Negative likelihood ratio: 0.5 (Zeren and Oztekin, 2006) |
| Passive range of motion test | Passive hip flexion: The patient is supine with the pelvis stabilized by grasping the iliac crest. As the hip is flexed, the knee is allowed to flex from the tension placed on the hamstrings and gravity. With pressure applied proximal to the knee joint, the normal end feel for hip flexion is soft owing to the approximation of the quadriceps with the abdomen. Passive knee extension: The patient is supine with the hip flexed to 90° and with the knee flexed in a relaxed position. The lower leg (below the knee) is passively extended to a firm muscle tension end point. | Reproduction of patient’s pain with either test | Sensitivity: 0.57 Specificity: 1.0 PPV: 1.0 NPV: 0.70 Positive likelihood ratio: 160.6 Negative likelihood ratio: 0.43 (Zeren and Oztekin, 2006)31 |
| Resisted range of motion test | Hip extension with an extended knee: the patient is prone, with the knee extended and the pelvis stabilized with pressure on the iliac crest. An isometric break test is performed at end-range hip extension, with resistance applied to the popliteal fossa. | Reproduction of patient’s pain with either test | Sensitivity: 0.61 Specificity: 1.0 PPV: 1.0 NPV: 0.72 Positive likelihood ratio: 170.6 Negative likelihood ratio: 0.4 (Zeren and Oztekin, 2006) |
Differential diagnosis of posterior hip pain
The differential diagnosis for posterior hip and thigh pain includes hamstring injuries, piriformis syndrome (also known as deep gluteal syndrome), ischiofemoral impingement, lumbar sciatic pain, ischial stress fractures, apophysitis, and local infection or malignancy. A few diagnoses outlined in Table 2 including common signs or symptoms help differentiate them from hamstring injuries. Special tests to consider, which may help ascertain other diagnoses, include the straight leg test; piriformis stretch test; and a combination of hip extension, adduction, and external rotation. Positive tests may suggest sciatica, piriformis syndrome, or iliofemoral impingement, respectively.
| Diagnosis | Pathology | Signs/Symptoms |
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| Proximal hamstring injuries | Range of disease from sprains to complete avulsions |
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| Piriformis syndrome (deep gluteal syndrome) | Extra-pelvic sciatic nerve compression by the piriformis muscle |
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| Ischiofemoral impingement | Impingement of soft tissues between the ischial tuberosity and lesser trochanter |
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| Lumbar radiculopathy | Sciatica due to compression on roots of the sciatic nerve by a herniated disc, spinal stenosis, etc |
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Imaging
Diagnostic imaging modalities include radiographs, ultrasound, and MRI. Patients with a suspected acute proximal hamstring injury may undergo a workup with an anterior-posterior radiograph of the pelvis to evaluate for a bony avulsion off of the ischial tuberosity, enthesopathy suggesting chronic changes, or other local bony pathology. However, plain radiographs are largely inconclusive for this diagnosis, which typically requires an ultrasound or MRI evaluation.
Musculoskeletal ultrasound is being increasingly used when resources and trained personnel are available. It is especially useful in the acute setting when MRI may not be readily available. When available, dynamic ultrasound (sonography) provides several advantages over radiographs, computed tomography (CT), and MRI, including decreased cost, portability, lack of ionizing radiation, dynamic soft tissue imaging, color Doppler or power Doppler imaging, and determination of focal tenderness to sonopalpation. , In a longitudinal study comparing sonographic and MRI assessments of acute and healing hamstring injuries, Connell and colleagues found that sonography has a similar sensitivity as MRI in depicting acute hamstring injuries, whereas MRI is more sensitive for follow-up imaging of healing injuries. Fig. 2 depicts normal and pathologic hamstring ultrasound images.
