This article provides an update on the current available evidence on the assessment, diagnosis, and prognosis of hamstring injuries in soccer. After a detailed insight into the epidemiology, functional anatomy, and injury mechanism for hamstring injuries, a detailed clinical examination, which is supported by clinical evidence, clinical experience and innovative practice, is demonstrated. Finally the recent Munich classification system is presented to improve clarity of communication for diagnostic, therapeutic and prognostic purposes.

By Wayne Gill BSc, MCSP

Epidemiology

Injury to the hamstring muscle group is frequently reported to be the most common injury in professional football representing 12% of all injuries (1). It has been reported that 83% of hamstring injuries affect the biceps femoris (BF) whereas 10% and 5% affect the semimembranosus and semitendinosus, respectively (2). A 25-player squad can expect five hamstring muscle injuries each season, resulting in 90 days and 15–21 matches missed per club per season (3). It’s been reported that 18 days and 3 matches are missed per hamstring strain, with a 12% re-injury rate (3). Re-injuries can lead to diminished athletic performance and frustration for the player (4). Injuries will also have a negative impact on the morale, performance, and results of the team, which can have huge financial implications for the club (4). Thus, hamstring strain injuries remain one of the most challenging injuries facing sports medicine practitioners.

Anatomy

The hamstring muscle group comprises semitendinosus (ST) and semimembranosus (SM) medially and the BF, short and long heads, laterally. All muscles attach proximally to the ischial tuberosity, except the BF short head, which originates at the linea aspera and lateral supracondylar line of the femur (5). The ST attaches to the medial surface of the superior tibia, SM to the posterior part of the medial condyle of the tibia and the oblique popliteal ligament, while the BF attaches to the fibular head. The BF also has strong fascial connections to peroneus longus at the fibula linking it to the action of the ankle and foot (6). Additionally, the SM has expansions extending to the knee joint capsule and the medial meniscus (Fig. 1; Video 1)(6).

Function

The hamstrings are biarticular (2-joint) muscles spanning the hip and knee joint with multiple attachments that allow them to affect function throughout the pelvis and lower extremities. The principle activities of the hamstring group are hip extension and knee flexion. However, the BF short head crosses only the knee joint and is therefore only involved in knee flexion. Additionally, with the knee in flexion the SM and ST can medially rotate the tibia, whereas the BF laterally rotates the tibia. The hamstrings are predominantly made up of Type II fast twitch fibres and are innervated by the tibial branch of the sciatica nerve. However, the BF short head is dually innervated by both the tibial and peroneal portion of the sciatic nerve (7). Functionally, the muscle group provides knee support during the early stance phase, propulsion during the mid to late stance phase and they control knee momentum during the swing phase (8). Studies of running biomechanics have found the hamstrings are active for the entire gait with peaks in activation during the terminal swing and early stance phases (9, 10). During the terminal swing phase the hamstrings are required to contract eccentrically to decelerate the flexing hip and extending knee in preparation for heel strike (11). Furthermore, using electromyography (EMG) analysis it’s been reported the BF is maximally activated between 15° and 30° of knee flexion, whereas the ST and SM are maximally activated between 90° and 105° of knee flexion (12). This indicates that the BF participates strongly during the terminal swing phase of running. Additionally, during the early stance phase the hamstrings have to absorb considerable force as a result of high ground reaction forces (10,11). Furthermore, the thoracolumbar fascia (TLF) via its extensive muscular attachments functionally connects the hamstrings to the lumbar-pelvic spine and the upper torso (6).

Injury mechanism

It has been reported that 70% of hamstring injuries in elite football players occur during high speed running and the rest with stretching, sliding, twisting, turning, passing, and jumping (13). The presence of high force eccentric contraction during the stance and swing phases likely contributes to the high rates of hamstring injuries during maximal speed running. The terminal swing phase is considered the most hazardous as the hamstring muscle tendon units are at their longest length of the gait cycle and are most heavily activated (11,14). This breaking force is often the point of muscle failure as the lengthening demands placed on the muscle exceed the mechanical limits of the muscle. There is some uncertainty as to whether hamstring injuries most typically occur as a result of the accumulation of microscopic muscle damage, or as a result of a single event (11). It seems feasible, however, that both may contribute. For example, the accumulation of microscopic damage as a result of repeated sprints may leave the muscle tissue in a vulnerable state and more susceptible to injury during a single traumatic event, such as kicking a ball (11).

Examination

History

Most soccer players with hamstring strain injuries present with a sudden onset of posterior thigh pain resulting from a specific action, most commonly high speed running (3). Players will often describe the occurrence of an audible pop or tearing sensation. However, a more gradual onset of hamstring pain may be more suggestive of a referred source, or what is commonly termed back-related hamstring pain (15). The lumbar spine especially at the L5/S1 levels, and the sacroiliac joints (SIJ) can refer pain to the posterior thigh especially if there has been a history of low back pathology (16). This type of hamstring pain that occurs during training is often due to increased loading of the lumbar spine. Therefore, an investigation into the training history could lead to important information regarding the causes of spine-related hamstring injuries. Additionally, myofascial trigger points (MTPs) from the gluteal muscles and the piriformis muscle may also refer pain into the hamstring region (17).

Palpation

Palpation of the posterior thigh is useful for identifying the specific muscle and location injured through pain provocation, as well as determining the presence/absence of a palpable defect in the musculotendinous unit (15). The point of maximal pain can be determined and located relative to the ischial tuberosity, in addition to measuring the total length of the painful region (15). Palpation also serves detect (superficial or larger) tears, perimuscular oedema and any increase in muscle tone (18). The examiner can also palpate the gluteal muscles to determine the presence of any MTPs which may also refer pain into the hamstring region. Additionally, the superior tibia-fibula joint (STFJ) should be assessed in hamstring injuries involving the BF (3).

Flexibility and neural tension

The Lasègue test otherwise known as the straight leg raise (SLR) test is commonly used to assess hamstring flexibility in soccer players (19). However, it’s suggested the SLR test has a dual function in measuring hamstring muscle length and assessing sciatic nerve mobility (20). Indeed, the SLR causes caudal movement of the sciatic nerve, and this stretching may cause a protective contraction of the hamstrings if there is entrapment of the sciatic nerve in the intervertebral canal due to disc prolapse, degenerative osteophytes, or other structures (21,22). Thus, in pathological states of the lower back, restriction may not be due to hamstring muscle injury, but muscle spasms in these muscles caused by irritation to the sciatic nerve (22). Despite this, the validity of the SLR test in the diagnosis of neural tension remains inconclusive (23). Due to the confusion about the SLR test, Gajdosik and Lusin (1993) designed the active knee extension (AKE) test to measure hamstring length by the angle of the knee flexion during AKE while the hip is stabilised at 90° flexion. Thus, the AKE is thought to be more selective than the SLR test at measuring hamstring length alone (24). Furthermore, the intra-tester reliability has been reported as high (25). The modified sit and reach (mSAR) test has been advocated as a general lumbar spine and hamstring flexibility test rather than a direct hamstring muscle length (19). The slump test is often used to assess adverse neural tension, and involves tensioning the neural system without additional hamstring stretch (26,27). The goal of the test is to differentiate nerve root pain from muscle pain (22). A positive test is defined as one which reproduces the symptoms during simultaneous knee extension and ankle dorsiflexion, and alleviated with cervical extension (27,28). The pain elicited by the slump test is thought to be due to excessive nerve stretch (intraneural), or reduced neural mobility at the interface with the surrounding muscle tissue (extraneural) (28). Recently, three flexibility tests have been advocated for diagnosing proximal hamstring tendinopathy (PHT), and these include the Puranen–Orava (PO) test, the bent-knee stretch (BK) test and the modified bent-knee stretch (MBK) tests. All three clinical tests are practical, easy to perform, and have demonstrated high validity and reliability for diagnosing PHT (29).

Strength

Hamstring strength can be evaluated in both the supine and prone positions. With the player in the prone position manual muscle testing (MMT) can be used to assess the isometric knee flexion strength initially at 90° (Fig. 2), then 45° (Fig. 3), and finally 15° (Fig. 4) of knee flexion. Additionally, the use of a hand-held dynamometer (HHD) can provide objective measurements and identification of any strength deficits at different knee flexion angles between the injured and non-injured side (30). With adequate stabilisation the HHD is a valid and reliable method of assessing hamstring strength (31, 32). Also, the concentric and eccentric hamstring strength can be assessed using manual resistance applied by the hands of the clinician. To place more emphasis on the BF it’s suggested the knee should be externally rotated, whereas internal rotation would bias the medial hamstrings (15). Because the hamstring muscles extend the hip it’s been recommended that hip extension strength be assessed with full knee extension and also knee flexion (15). The elevated single leg bridge test is a quick and simple way of assessing hip extension and can be performed with the knee fully extended and also flexed (Figs 5, 6; Video 2). Collectively, the aforementioned strength tests will provide the examiner with subjective and objective markers which can be used to monitor the progression and recovery throughout the rehabilitation process.

Lumbar spine and pelvis

The pelvis provides a dynamic link between the trunk, vertebral column, and the lower limbs and has been described as the keystone for both movement and support (33). Therefore, asymmetry or dysfunction within pelvic structures can alter movement patterns resulting in less efficient movement, and alterations in joint forces and muscle function (34). Due to the anatomical and functional relationship with the pelvis the hamstrings may be vulnerable to injury. Excessive anterior tilt of the pelvis due to sacroiliac joint (SIJ) dysfunction will increase the muscle length and tension within the hamstring muscles, thus predisposing them to injury (35,36). The function of the SIJ may be assessed by a number of kinetic tests, including the stork test (also known as the Gillet test) and the forward flexion test (37). Additionally, the position of the pelvis should be examined to determine the presence of any postural asymmetries which may also indicate a true or apparent leg length discrepancy (38,39). The lying/sitting test is a clinical method frequently used to differentiate between a true and apparent leg length discrepancy (40). The active straight leg raise (ASLR) test has recently been used as a screen of lumbar spine stability to assess the control of lumbar rotational movements in the transverse plane (41). Good control without anterior pelvic tilt is required and excessive anterior pelvic tilt typically accentuates the lumbar lordosis and can be a sign of poor stabilisation of the pelvis by the abdominal muscles (6, 30). Therefore, a thorough biomechanical evaluation of the lumbar spine, SIJ, and the pelvis should be included as part of the injury assessment.

Diagnosis

The diagnosis is based on the clinical history, examination findings, and the use of imaging modalities such as ultrasound and magnetic resonance imaging (MRI). An early post-injury ultrasound between 2 and 48 hours has been advocated as it can provide helpful information about any existing disturbance of the muscle structure, particularly if there is any haematoma (18). However, MRI is considered superior for evaluating injuries to deep portions of the muscles, or when a previous hamstring injury is present, as residual scarring can be misinterpreted on an US image as an acute injury (42). Furthermore, due to its increased sensitivity in showing subtle oedema, measuring the size (length and cross sectional area) and site of injury including any tendon involvement, MRI is more accurate (42). Thus, an MRI examination within 24–48 hours of the injury event should be performed (2, 18).

Classification

Currently the most widely used classification for hamstring injuries is an MRI based graduation defining four grades: grade 0, no visible pathology; grade 1, oedema but no architectural distortion; grade 2, partial tear with architectural disruption; and grade 3, total muscle or tendon rupture (2). Around 70% of hamstring injuries seen in professional football are of radiological grade 0 or 1, meaning no signs of fibre disruption on MRI. However, these injuries caused more than 50% of the absence of players in clubs (2). The actual cause of posterior thigh injury where MRI shows no pathology is unclear, but may be due to an alternative diagnosis. Recently the Munich muscle injury classification was introduced as a new terminology and classification system of muscle injuries (18). This clinical tool can be used to assist diagnosis by classifying muscle injuries into functional and structural injuries. Functional disorders are fatigue induced or neurogenic injuries causing muscle dysfunction without microscopic evidence of fibre tear, while structural injuries are tears of muscle fibres (Table 1). In elite professional football it has been reported that 65% of hamstring injuries are structural injuries and 35% are functional disorders (43).

Prognosis

The ability to predict lay-off time is very important for the injured player as well as the coaching staff. Recent studies evaluating the use of MRI have demonstrated that MRI abnormalities can not only confirm the clinical diagnosis, but also provide a reasonable estimate of the rehabilitation period (2,44). Ekstrand et al. (2012) assessed the prognostic value of MRI by grading the severity of 516 hamstring injuries in football players (Table 2)(2). Additionally, Ekstrand et al. (2013) recently demonstrated the Munich muscle classification can be used by clinicians to prognosticate return to play after a muscle injury in football players (Table 3)(43).

The Munich classification clearly shows a difference in return to play between structural and functional muscle injuries. This seems logical since by definition structural injuries show macroscopic evidence of muscle fibre damage, and functional disorders show no such damage (18). Establishing the type of injury also provides essential prognostic information since a stretching-type of injury has, on the average, 84% longer times (59 vs 32 days) to return than a sprinting-type of injury (43). Other measurements with similar prognostic value, that is, prolonging or shortening the time to return, are position of peak pain upon palpation in relation to the ischial tuberosity as well as oedema length upon MRI. The shorter the distance to the ischial tuberosity and the longer the length of the oedema have been associated with longer recovery times (43). Hamstring tears >60mm (6cm) in length or >10% cross sectional area (CSA) have been shown to have a recovery time of at least 3 weeks (45,46). Additionally, more than 1 day of walking with pain has also been associated with a recovery time of at least 3 weeks (46). Injuries involving disruption to tendinous tissue (central or proximal free tendons) have a significantly worse prognosis than injuries which involve only muscle fibres, epimysial fascia, or the musculotendinous junction (44). This may be reflective of the increased remodelling time required of tendinous injuries. Therefore, the length of rehabilitation is proportional to the classification, location, and severity of injury.

Summary

This article provides the reader with an update on the current available evidence on the assessment, diagnosis, and prognosis of hamstring injuries in football. The diagnosis is based on the clinical history, examination findings, and the use of imaging modalities such as ultrasound and MRI. The Munich classification tool has been introduced to assist diagnosis by classifying muscle injuries into functional and structural injuries and improve clarity of communication for diagnostic, therapeutic and prognostic purposes.

Discussions

1. Describe the function of the hamstrings during the gait cycle.
2. What is the most common injury mechanism for hamstring injuries?
3. Which clinical tests would you use to assess hamstring muscle flexibility and neural tension?
4. Describe the different types of functional and structural disorders associated with the Munich classification.

Continuing education quiz

This article also has a certificated eLearning assessment that can be found in the Media Contents box, or under the eLearning Assessment area in your Account area, on the Co-Kinetic website. The eLearning assessment(s) can be completed on all platforms including mobiles when accessed through the Co-Kinetic site; however, they are NOT accessible through the sportEX mobile app as you have to be logged into the actual website for the results to be recorded and the certificate to be generated.

Quotations/important points

“Hamstring Injuries remain one of the most challenging injuries facing sports medicine practitioners”

“The diagnosis of hamstring injuries should be based on clinical history, examination findings, and the use of imaging modalities”

“The Munich muscle injury classification can be used to assist diagnosis by classifying hamstring injuries into functional or structural injuries”

“The Munich classification can be used by clinicians to prognosticate a return to play for football players”

References

1. Ekstrand J, Hagglund M, Walden M. Injury incidence and injury patterns in professional football: the UEFA injury study. British Journal of Sports Medicine 2011;45:553–558
2. Ekstrand J, Healy J, et al. Hamstring muscle injuries in professional football: the correlation of MRI findings with return to play. British Journal of Sports Medicine 2012;46:112–117
3. Woods C, Hawkins R, et al. The Football Association Medical Research Programme: an audit of injuries in professional football – analysis of hamstring injuries. British Journal of Sports Medicine 2004;38:36–41
4. Liu H, Garrett W, et al. Injury rate, mechanism, and risk factors of hamstring strain injuries in sports. A review of the literature. Journal of Sport and Health Science 2012;1:92–101
5. Ali K, Leland M. Hamstring strains and tears in the athlete. Clinics in Sports Medicine 2012;31:263–272
6. Hoskins W, Pollard H. The management of hamstring injury – part 1: issues in diagnosis. Manual Therapy 2005;10:96–107
7. Gray H. Gray’s anatomy: the anatomical basis of clinical practice. Standring S (ed.), Section 9, pp1377. Churchill Livingston 2008. ASIN B00A357QUE. View on Amazon
8. Adebe E, Moorman CT, Garrett WE. Proximal hamstring avulsion injuries: injury mechanism, diagnosis and disease course. Operative Techniques in Sports Medicine 2012;20:2–6
9. Yu B, Queen R, et al. Hamstring muscle kinematics and and activation during overground sprinting. Journal of Biomechanics 2008;14(41):3121–3126
10. Chumanov E, Heiderscheit B, Thelen D. Hamstring musculotendon dynamics during stance and swing phase phases of high speed running. Medicine & Science in Sports & Exercise 2011;43(3):525–532
11. Opar D, Williams M, Shield A. Hamstring Strain Injuries. Factors that lead to injury and re-injury. Sports Medicine 2012;43(3):209–226
12. Onishi H, Yagi R, et al. EMG-angle relationship of the hamstring muscles during maximum knee flexion. Journal of Electromyography and Kinesiology 2002;12:399–406
13. Ekstrand J, Healy J, et al. Hamstring muscle injuries in professional football: the correlation of MRI findings with return to play. British Journal of Sports Medicine 2012;46:112–117
14. Thelen D, Chumanov E, et al. Hamstring muscle kinematics during treadmill sprinting. Medicine & Science in Sports & Exercise 2005;37(1):108–114
15. Heiderscheit B, Sherry M, et al. Hamstring strain injuries: Recommendations for diagnosis, rehabilitation and injury prevention. Journal of Orthopaedic & Sports Physical Therapy 2010;40(2):67–81
16. Orchard J, Farhart P, Leopold C. Lumbar spine region pathology and hamstring and calf injuries in athletes: is there a connection? British Journal of Sports Medicine 2004;38:502–504
17. Asher S. The concise book of trigger points, 2nd edn, pp148–159. Loftus Publishing 2008. ISBN 1556437455. View on Amazon
18. Mueller-Wohlfahrt H, Haensel L, et al. Terminology and classification of muscle injuries in sport; The Munich consensus statement. British Journal of Sports Medicine 2013;47:342–350
19. Rolls A, George K. The relationship between hamstring muscle injuries and hamstring muscle length in young elite footballers. Physical Therapy in Sport 2004;5:179–187
20. Dixon J, Keating J. Variability in Straight Leg Raise Measurements. Physiotherapy 2000;86(7):361–370
21. Ylinen J, Kautiainen H, Hakkinen A. Comparison of Active, Manual, and Instrumental Straight Leg Raise in Measuring Hamstring Extensibility. Journal of Strength and Conditioning Research 2010;24(4):972–977
22. McHugh M, Johnson C, Morrision R. The role of neural tension in hamstring flexibility. Scandinavian Journal of Medicine & Science in Sports 2012;22:164–169
23. Capra F, Vanti C, et al. Validity of the straight leg raise test for patients with sciatic pain with or without lumbar pain using magnetic resonance imaging results as a reference standard. Journal of Manipulative Physiology Therapy 2011;34:231–238
24. Gajdosik R, Lusin G. Hamstring muscle tightness: reliability of the active knee extension test. Physical Therapy 1983;63(7):1085–1090
25. Gajdosik R, Rieck M, et al. Comaprison of four clinical tests for assessing hamstring muscle length. Journal of Orthopaedic Sports Physical Therapy 1993;18(5):614–618
26. Kornberg C, Lew P. The effect of stretching neural structures on grade one hamstring injuries. Journal of Orthopaedic Sports Physical Therapy 1989;10:481–487
27. Miller K. The slump test: Clinical applications and interpretations. Chiropractic Technique 1999;11(4):157–163
28. Turl S, George K. Adverse neural tension: a factor in repetitive hamstring strain? Journal of Orthopaedic Sports Physical Therapy 1998;27:16–21
29. Cacchio A, Borra F, et al. Reliability and Validity of three pain provocation tests used for the diagnosis of chronic proximal hamstring tendinopathy. British Journal of Sports Medicine 2012;46:883–887
30. Mendiguchia J, Brughelli M. A return to sport algorithm for acute hamstring injuries. Physical Therapy in Sport 2011;12:2–14
31. Kelln B, McKeon P, et al. Hand-held dynamometry: Reliability of lower extremity muscle testing in healthy, active, young adults. Journal of sport rehabilitation 2008;17:160–170
32. Trudelle-JacksonE, Jackson A, et al. Interdevice reliability and validity assessment of the Nicholas hand held dynamometer. Journal of Orthopaedic & Sports Physical Therapy 1994;20(6):302–306
33. Lee D. The pelvic girdle: an approach to the examination and treatment of the lumbopelvic-hip region, 3rd edn, pp41–61. Churchill Livingston 2004. ISBN 0443073732. View on Amazon
34. Sahrmann S. Diagnosis and treatment of movement impairment syndromes, pp74–84. Mosby 2002. ISBN 0801672058, View on Amazon
35. Cibulka M, Rose S, et al. Hamstring muscle strain treated by mobilizing the sacroiliac joint. Physical Therapy 1986;66(8):1220–1223
36. Hennessy L, Watson A. Flexibility and posture assessment in relation to hamstring injury. British Journal of Sports Medicine 1993;27(4):243–246
37. Wurff P, Hagmeijer R, Meyne W. Clinical tests of the sacroiliac joint – part 1: reliability. Manual Therapy 2000;5(1):30–36
38. Herrington L. Assessment of the degree of pelvic tilt within a normal asymptomatic population. Manual Therapy 2011;16:646–648
39. Gurney B. Leg length discrepancy. Gait Posture 2002;15:195–206
40. Bemis T, Daniel M. Validation of the long sitting test on subjects with iliosacral dysfunction. Journal of Orthopaedic & Sports Physical Therapy 1987;8(7):336–345
41. Liebenson C, Karpoowicz A, et al. The American Academy of Physical Medicine and Rehabilitation 2009;1:530–535
42. Connell D, Schneider-Kolsky M, et al. Longitudinal study comparing sonographic and MRI assessments of acute and healing hamstring injuries. American Journal of Roentgenology Diagnostic Imaging and Related Sciences 2004;183(4):975–984
43. Ekstrand J, Askling C, et al. Return to play after thigh muscle injury in elite football players: implementation and validation of the Munich muscle injury classification. British Journal of Sports Medicine 2013;47:769–774
44. Comin J, Malliaras P, et al. Return to Competitive Play after hamstring injuries involving disruption of the central tendon. The American Journal of Sports Medicine 2013;41(1):111–115
45. Gibbs N, Cross T, et al. The accuracy of MRI in predicting recovery and recurrence of acute grade one hamstring muscle strains within the same season in Australian Rules football players. Journal of Science and Medicine in Sport 2004;7(2):248–258
46. Warren P, Gabbe B, et al. Clinical predictors of time to return to competition and of recurrence following hamstring strain in elite Australian footballers. British Journal of Sports Medicine 2010;44:415–419.