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Training, Prevention, and Rehabilitation: Section Articles

Rehabilitation and Prevention of Proximal Hamstring Tendinopathy

Beatty, Nicholas R. DO, MS1; Félix, Ioonna PT, DPT, OCS, CTPS2; Hettler, Jessica PT, DPT, ATC, Cert MDT, SCS2; Moley, Peter J. MD1; Wyss, James F. MD, PT1

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Current Sports Medicine Reports: 5/6 2017 - Volume 16 - Issue 3 - p 162-171
doi: 10.1249/JSR.0000000000000355
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Abstract

Introduction

Proximal hamstring tendinopathy (PHT) is a challenging clinical entity comprising a small but significant portion of hamstring injuries in athletes (11,15). Distinct from the more commonly encountered acute hamstring strain, PHT is a chronic, overuse condition that develops from mechanical overload and repetitive stretching of the proximal hamstring. Therefore, there is gradual or insidious onset of symptoms. PHT is a tendinopathy affecting the semimembranosus and/or biceps femoris/semitendinosus complex. PHT predominantly affects middle- and long-distance runners, sagittal plane dominant athletes, and individuals (including nonathletes) who routinely perform activities that compressively load the proximal hamstring attachment such as squatting, lunging, changing direction of running, leaning forward, sitting for long periods, and excessive static stretching (11,15,34).

Further understanding of the etiology of PHT is best derived from the tendinopathy literature and is considered multifactorial (15,18,20,21,34). Potentially modifiable risk factors of tendinopathy include failure to adapt to new or increasing work load or volume, inefficient biomechanics, incomplete recovery, body mass index, sport or movement demands, medications (40,68), and reversible systemic disease. Nonmodifiable risk factors included advancing age, genetics (67,70), prior injury, and anatomic variation.

PHT is a clinical diagnosis made largely in part by a detailed history and examination (1,7,12,13), supported with diagnostic imaging including magnetic resonance imaging (MRI) and musculoskeletal ultrasound (25,63,74,78). There is very little scientific evidence on which to base the management of PHT. Treatment is almost always conservative with surgery limited to recalcitrant cases or those involving concomitant acute or chronic high-grade musculotendinous or nerve pathology (8,43,44). Nonoperative treatment may include physical therapy, activity modification, and ultrasound-guided interventional procedures. The general approach to PHT management includes early and accurate diagnoses, rehabilitation focused on a safe return to preinjury activity level, and ongoing training methods seeking to minimize reinjury (36,66). The purpose of this article is to critically review the recent literature regarding the prevention and rehabilitation of PHT, including the anatomy, etiology, and work-up of PHT.

Anatomy

Three of the four hamstring muscles of the posterior thigh (semitendinosus, semimembranosus, and the long head of the biceps femoris) attach proximally to the ischial tuberosity, span and act on two joints (i.e., extension at the hip and flexion at the knee) and are innervated by the tibial division of the sciatic nerve (Fig. 1) (27,53). The short head of the biceps femoris is innervated by the common fibular division of the sciatic nerve, attaches proximally to the linea aspera and supracondylar line of the femur, and functions as a hamstring muscle in the context of knee flexion. Functionally, the hamstrings play an important eccentric role in the gait cycle by decelerating knee extension during terminal swing phase (6).

Figure 1
Figure 1:
Posterior view of the right ischial tuberosity illustrating proximal hamstring anatomy and the sciatic nerve. ST, semitendinosus; BFlh, biceps femoris long head.

The long head of the biceps femoris and the semitendinosus share a common proximal conjoint tendon that arises from the medial facet of the ischial tuberosity (11,39). Semitendinosus muscle fibers originate medially from the conjoint tendon at the ischial tuberosity, whereas fibers from the long head of the biceps femoris arise laterally from the conjoint tendon and more proximally. The proximal attachment of the semimembranosus tendon arises from the lateral facet of the ischial tuberosity. This tendon arrangement is important to consider diagnostically in PHT because the conjoint tendon and semimembranosus tendon are often injured separately or to different degrees of severity and therefore, treatment should address the appropriate pathologic tendon. Pathoanatomical findings in PHT may involve the semimembranosus (33) and/or biceps femoris (7) tendons, but injury patterns are not as well described as in hamstring strains (i.e., type I injuries typically involve the long head of the biceps femoris; type II injuries involve the semimembranosus) (12,13).

Tendinopathy

The process underlying tendinopathy has been better characterized over the last few decades (4,32,46), and there are several models that seek to explain the pathohistological process. Tendinopathy has traditionally been attributed to chronic tensile overloading and/or inefficient loading, characterized by a loss of normal tendon architecture, incomplete healing, and a cyclical pathologic loading response (31,47). In addition to increased tensile forces causing tendon overload, the notion that compressive load alters the composition of tendon was revisited by Cook and Purdum in 2012 (20) and ushered in the modern framework for how tendinopathy is diagnosed and rehabilitated. Tendons can withstand large tensile loads but less so compressive loads, in which tendon is compressed at its bony attachment, similar to the compression of a cable wrapping around a pulley. This can occur in any tendon that abuts a bony protuberance during functional activities or sport, such as the Achilles tendon in end-range dorsiflexion. When the proximal hamstring tendon wraps around the ischial tuberosity during end-range hip or trunk flexion, there is a resultant compressive load which has been associated with tendinopathic changes. Therefore, repetitive stretching of the tendon may lead to PHT and a rehabilitation approach that focuses exclusively on overstretching will fail. However, tendon also can become pathologic without loading (i.e., stress shielding) in the presence of certain risk factors. There may be a continuum of pathology including normal tendon, reactive tendinopathy, and tendon dysrepair, with opportunity for repair in the earlier stages (20). The relationships between tendon degeneration, function, and pain are even more complex and involve central sensitization, lending support for rehabilitation that incorporates externally paced resistance training, coined tendon neuroplastic training (65). Despite these recent advancements, there is significantly more to decipher in both the mechanism and management of tendinopathy.

Diagnosis

Clinical Presentation

A thorough history and physical examination is key to arriving at the correct diagnosis of PHT. While PHT has a unique presentation, it shares a similar phenotype to tendinopathy in general in that the onset of symptoms is insidious. The main presenting complaint is pain in the lower gluteal region that may or may not radiate along the hamstrings in the posterior thigh (42). Commonly, the symptoms will present upon starting exercise and resolve after warming up. The symptoms often return upon completion of exercise. Early on, pain may arise only with peak effort or competitive play. As the condition progresses, the pain does not resolve with warming up or with continued exercise, persists after exercise, and very often is noticeable with activities of daily living and even at rest (34), especially with sitting and driving. Because pain with sitting and/or driving is a hallmark finding in PHT and also will occur with lumbosacral radiculopathy, the physical examination becomes vital in distinguishing between these two clinical entities. Sciatic nerve involvement and related symptoms are sometimes involved due to the proximity of the tendons to the sciatic nerve (22,44,49). Attention should focus beyond just the musculoskeletal history of present illness (e.g., medical history, medications, social history) to review the modifiable and nonmodifiable risk factors for PHT.

Clinical Examination

Examination should not only lend support to the presence of PHT but also rule out referred pain from the lumbosacral spine, hip, and nearby neurovascular and myofascial pain generators; therefore, a thorough screen of the lumbosacral spine, pelvis, and corresponding neurological examination is vital. The premise of the hamstring examination is to apply a stretching force across the hamstring muscle group through end-range of motion maneuvers to elicit a provocative painful response or apprehension. Three maneuvers are reported in the literature: the Puranen-Orava test (61), an active standing straight-leg hamstring stretch with the hip flexed at 90 degrees; the Bent Knee Stretch Test, a passive supine test with the hip remaining in flexion and the knee is then provocatively extended (13); and the Modified Bent Knee Stretch Test, a passive supine test in which the subject’s extended leg is brought into hip and knee flexion followed by rapid knee extension. Nevertheless, there remains a need for more research into special tests for diagnosing hamstring injuries (64). The examiner should use physical examination techniques to provoke symptoms with resisted contraction and passive stretch positions and an accurate palpatory examination. There is often focal tenderness of the proximal hamstring tendon(s) at the ischial tuberosity. There also may be a relative reduction in hamstring strength, possibly due to pain limitations. Resisted hip extension with the knee flexed is an ideal way to test gluteus maximus function during examination of the patient in the prone position and can provide insight into biomechanical causes of PHT, such as lumbopelvic weakness. Except in the setting of concomitant sciatic nerve irritation which is a less common feature in PHT cases, the neurologic examination should be intact.

Role of Imaging

Imaging may be helpful to confirm the presence of the anticipated pathology based on the history and examination. While symptoms do not always align with severity of PHT, imaging is useful in assessing the extent of tendinopathy present and in ruling out other pathology (i.e., muscle or myotendinous strain, avulsion, neurovascular injury, lumbopelvic pathology, or myofascial defect). MRI and ultrasound are the modalities of choice (45,78). MRI is more sensitive in detecting tendinopathy of the proximal hamstrings (78) with noted increased signal on T1/T2, tendon thickening, and peritendinous and ischial bone marrow edema. Ultrasound has the advantages of being readily available at the point-of-care, providing dynamic evaluation, confirming the site of maximal tenderness (sonopalpation), and measuring interval follow-up of ultrasound findings for rehabilitation and management (58). Ultrasound findings include tendon thickening, peritendinous fluid, hypoechoic or heterogeneous echotexture, echogenic foci of calcific tendinopathy, cortical irregularity, and concordant pain. Normal tendon findings may lend support for an alternative diagnosis. With any imaging investigation, it is crucial to remember that many asymptomatic individuals will present with pathology on MRI (25,71) and ultrasound (78). Judicious use of imaging to strengthen the evidence for a suspected diagnosis and assist with management is the sound approach.

Differential Diagnoses

The differential diagnoses in PHT includes partial or complete tendon rupture with or without avulsion, myotendinous junction injury, hamstring, adductor magnus, or gluteal muscle strain (76), posterior ischial stress reaction, ischiofemoral impingement (28), sciatic nerve irritation, hip osteoarthritis, or femoroacetabular impingement presenting with lower gluteal pain, lumbosacral radiculopathy, lumbosacral facet-mediated referred pain, and ischial bursopathy. It is important to consider that there may be multiple concomitant problems, particularly in the setting of prior injury or advanced tendinopathy.

Physician Decision-Making and Initial Rehabilitation Management

Early recognition and treatment is the initial key to successful rehabilitation. Imaging that confirms the concordant tendinopathic conjoint or semimembranosus tendon and rules out other neighboring pathology is reassuring and can help solidify the treatment plan. However, like other chronic overuse or intermittent-use injuries, failure to alter the demands on the tendon will ensure a prolonged and incomplete recovery and increase the likelihood of reinjury. It is therefore paramount for the treating physician to put in place a definitive and comprehensive plan that includes patient education, activity modification, rehabilitation with a professional experienced in tendon rehabilitation, and regularly scheduled follow-up evaluation. The decision to perform a therapeutic intervention or needle procedure should be made within an evidence-informed framework, whether it be a continuum model or clinical experience. When rehabilitation stalls, a change in the rehabilitation plan is necessary and should be carried out quickly to avoid a prolonged return to play. Change may include reinforcement of commitment from the athlete to the rehabilitation program, a different approach to therapy, or referral to a medical or surgical colleague when indicated. Equally important to the initial plan is thinking ahead of how the plan will change based on the rehabilitation progress.

Rehabilitation

Overview of Rehabilitation Approach

Before our understanding of tendon pathology and the complex musculotendinous anatomy of the posterior thigh, most hamstring injuries were grouped together in terms of both diagnosis and treatment (3). In recent decades, improved diagnostic imaging techniques and an increase in musculoskeletal research has improved our ability to describe muscle, tendon, nerve, and bony injury. Our approach has predominantly focused on early diagnosis and conservative management, intended to correctly identify the pathoanatomy and etiology at the onset of presenting complaints, and to direct treatment accordingly. When PHT transitions from a focal injury to a more complex chronic musculoskeletal condition with concomitant regional dysfunction, treatment becomes more challenging. Compensatory movement affords activity with less pain but compromises movement quality. With time, PHT involves impairments in strength, muscle recruitment and firing, control, flexibility and endurance (5). The rehabilitation approach for PHT includes a global assessment of function and comprehensive treatment of impairment within the context of the specific hamstring tendinopathy, underlying the importance of an accurate diagnosis at the onset. Selective functional movement assessments can further identify dysfunctional movements not seen with more conventional examination procedures (31). Squats, lunges, and arabesque position can provide additional information. An important goal of tendon rehabilitation is to identify more regional, global, or central processes in the kinetic chain that may have initially contributed to the hamstring tendon failed load transfer or may have subsequently been effected by inefficient or pathological hamstring function (37).

Biomechanical Considerations

Identifying and addressing biomechanical inefficiencies may enhance rehabilitation, although it should be carried out within the context of the primary goal of load management, and with acknowledgement of the inherent variability in biomechanics amongst individuals. Postural dysfunction has been proposed to contribute to the development of PHT, although this has not been fully studied. This includes an anterior pelvic tilt in both static and dynamic positions, due in part to reduced flexibility of the hamstrings, hip flexors, and quadriceps. An anterior pelvic tilt has been found to increase the demand on the hamstrings (40). In particular, the biceps femoris tendon is compressed in this position. Addressing hip flexor/quad tightness and myofascial restrictions can help to correct an anterior pelvic tilt, thereby reducing hamstring tension.

Muscle imbalances and asymmetry are often present in the setting of PHT, although there is no evidence on whether imbalances increase risk for PHT or whether they arise due to PHT. Individuals frequently exhibit reduced or deficient hip extension, substantial heel strike in gait or running, and excessively long stride and forward trunk lean. Overactivation of the hip flexors and inhibition of the gluteus maximus are present in this population (49). With inefficient gluteal activation, the hamstrings assume a prominent role in hip extension which can lead to overuse.

Evaluation of the athlete’s stretching practices may give insight into tendinopathy. Static hamstring stretching has historically been prescribed as treatment for these disorders, but in many cases, has contrary effects on the tissue and can even increase an individual’s pain (40). Depending on the degree of hip flexion, static stretching can increase the compression load on the tendon and lead to PHT. Clinically, more successful outcomes in improving flexibility of the lower extremities have included dynamic and eccentric exercises (57) which may be an effective stretching strategy in maintaining lower extremity flexibility without increasing the compressive load.

Provocative loading tests are used to reproduce symptoms by increasing the tensile and compressive load to the proximal hamstring tendon by varying the angle of hip flexion and can be used in both assessment and treatment with minimal to maximal resistance. A typical biomechanical progression includes single-leg bent knee bridge, long-lever bridge, arabesque, and the single-leg Romanian deadlift (31).

Rationale for Program Design

Rehabilitation of PHT should focus on increasing load tolerance in a multimodal stepwise approach, addressing biomechanical deficits, improving posture, neuromuscular training, strengthening of the core and hip musculature, eccentric hamstring strengthening, and optimization of sport-specific and skill-related movement. Therapeutic modalities and manual therapies, such as soft tissue mobilization, are appropriate adjunctive therapies if they are needed to help relieve pain, overcome muscle inhibition, or to restore mobility of tight and shortened tissue that cannot be accomplished by therapeutic exercise alone.

Although the literature on the rehabilitation of tendinopathy has focused primarily on the Achilles tendon (3), patellar tendon, and the common extensor tendon of the wrist, and not specifically on hamstring tendons, we can still gain insight from this literature and apply in the rehabilitation of PHT. Eccentric exercise results in less oxygen consumption, greater force production, and less energy expenditure than concentric exercise. Eccentric exercises for tendinopathy promote cross linkage of collagen fibers within the tendon and subsequent remodeling (42). Common eccentric strengthening exercises that are incorporated in different phases of rehabilitation for PHT include: Nordic Hamstring Exercise, deadlifts, split squat/Bulgarian squats, eccentric backward steps, eccentric forward pulls, and eccentric lunge drops (Fig. 2).

Figure 2
Figure 2:
Exemplary rehabilitation exercises for PHT. Top, single-leg bent-knee bridge; bottom left, Nordic hamstring exercise; bottom right, single-leg contralateral reach/diver.

Bourne et al. (10) investigated the impact of exercise selection on hamstring muscle activation using EMG and found that hip-extension exercises selectively activate the long hamstrings and the Nordic exercise preferentially recruits the semitendinosus. Although the hamstring is a two-joint muscle, eccentric training has focused primarily on resisted knee flexion with less focus at the hip. Recent investigation looked at hip extension versus Nordic Hamstring Exercise in increasing biceps femoris long head fascicle length and found both hip and knee-based exercises were effective, although there was more hypertrophy with hip-based exercise (9). One case report demonstrates a positive outcome in a runner using retrotreadmill training with the emphasis on eccentric hip extension while maintaining a neutral pelvis (22). While it is hypothesized that eccentric exercises with a component of hip flexion will lead to greater adaptation in musculotendinous architecture and function (35), there is no supportive evidence to date.

Rehabilitation Goals

The two main goals of a PHT rehabilitation program are: 1) return the athlete safely and expeditiously to preinjury level of activity, and 2) prevent reinjury. How one goes about meeting these goals is variable, and it is probable that we have yet to solidify an ideal evidence-based program or framework. The more traditional guidelines are linear and tend to be time and criteria-based phases of care with phase-based exercise restrictions and goals per stage (36,72), similar to the more predictable postoperative rehabilitation protocols. More recent alternative guidelines under investigation have flattened the exercise hierarchy to expose the athlete to low-load dynamic movements earlier (56). In doing so, the goal of pain-free phase 1 exercises is removed which is often the longest and sometimes prolonged phase. This potentially shortens the amount of time used for low-level exercises and allows for more time working on the level of exercises that are needed for return to play. The theoretical result with the alternative guideline is a quicker return to play, more exposure to exercises that improve tendon architecture, reduce pain, and lower reinjury rates. More large-scale research is required to determine the safety and efficacy of a flattened approach. We will review the common features of the hierarchical guidelines. Of note, it is important to recognize that rehabilitation guidelines for overuse injuries (e.g., tendinopathy) are often adopted from acute injury (e.g., strain or surgery) guidelines and therefore should always be scrutinized and customized accordingly.

Phase 1

The first phase of a PHT rehabilitation program is directed at reducing pain, irritation, and barriers to participation. The treatment consists of relative rest, ice, core/proximal hip strengthening, and education on activity modifications that includes reduction and/or cessation of sport. Isometric exercises are used heavily in this phase of care. Isometric exercises allow activation of the hamstring without compression at its proximal attachment. Gluteal and hamstring activation is initiated with isometric hip extension. Research by Rio et al. (65) found holds of 30 to 60 s for three to four repetitions successful in decreasing pain and initiation load on the myotendinous unit. An abdominal/hip strengthening program is initiated from the beginning of therapy with the goal of unloading the hamstrings during functional activities (28). The rehabilitation should take into consideration a gradual progressive loading of the tendon. Therapeutic treatments are frequently used to promote analgesia, such as soft tissue work, dry needling, Graston, and cupping techniques (41), all of which are deemed safe but without strong evidence for PHT.

Phase 2

The second phase is frequently initiated when the individual can perform isometric exercises without pain and tolerate walking/biking/jogging. Now, concentric contractions are introduced and the load and hip/knee position is stressed. Typically, the individual begins with three to four sets of 10 to 15 repetitions of each exercise per day, a load-volume framework based on earlier efficacious Achilles tendinopathy research (3). It is normal to experience some pain during and after the exercises as long as it resolves after a few hours. With high loading exercises, such as lunging, the pain should subside in a day period, and progression of the rehabilitation program should be delayed until the athlete has full recovery from the prior session.

Phase 3

After both isometric and concentric exercises are well tolerated while positioned in a neutral pelvis, the third phase of rehabilitation includes more advanced hip flexion. The rehabilitation focus becomes an eccentric and ongoing concentric loading of the tendon. These exercises include supine leg curls (bilateral or unilateral), single leg bridge progressions, hip biased deadlifts, and Nordic hamstring exercises. Improving the strength, power, and endurance of the gluteus maximus in many of these exercises will decrease the dominance of the hamstrings. Another important aspect of eccentric training is alternate-day loading with off day recovery regimen. Goom et al. (34) noted that the optimal training schedule will include a 3-d loading cycle (high, low, medium) repeated twice per week with 1 d of rest between the cycles. Functional outcome measures, such as the Victorian Institute of Sports Assessment-Proximal Hamstring Tendons, can indicate the severity of function and symptoms as well as the ability to play sports (14).

Phase 4

Once the individual is able tolerate increased functional and energy storage loads on the hamstring in variable positions of hip flexion (e.g., long lever bridge and arabesque exercises), high-velocity plyometric exercises can be introduced in the fourth stage of rehabilitation. The rehabilitation emphasis should continue to focus on lumbopelvic control in multiplanes in bilateral and single leg tasks. Plyometrics and sport-specific activities are designed to increase hamstring torque and lower extremity power. The selection of specific plyometric and multiplanar exercises should consider the demands of the sport and be individually tailored to the athlete. Examples of plyometric exercises include: A skips and B skips, squat jumps, sled push, split jumps, bounding and depth jumps. It is recommended to perform three to four sets of these exercises. If an individual is returning to running, it is important to reassess running mechanics. Hill running is highly provocative and should be held until the end of therapy and the person has returned to flat course running. Throughout each phase of the rehabilitation, there must be an emphasis on neuromuscular and neuroplasticity training where the individual focuses attention on quality movement. This helps to create new movement strategies and pathway connections throughout the central nervous system.

Return-to-Play

The final phase of rehabilitation is return to sport. Preparing an athlete to return-to-play requires sport-specific rehabilitation to meet the demands of that sport. Sport-specific rehabilitation should only be initiated when the athlete is asymptomatic and has demonstrated full strength, endurance, control, stability, and mastery of fundamental movements and movement patterns like squatting, cutting, and sprinting without any compensational movements. Sport-specific exercises include single leg bounding, backward skips, lateral hops, lateral bounding, zigzag hops, running and cutting, and downhill running.

The limited evidence in clinical management of PHT coupled with the lack of data on return-to-play criteria can make an individual’s return to sport a daunting task for any multidisciplinary team. Current research on return to play guidelines only necessitates asymptomatic full range of motion and strength as the minimal criteria. This is likely underestimating the demands of sport and providing disservice to the athlete. There is no validated return-to-play test for PHT. One test used for return-to-play in the hamstring strain population is the H-test (6). H-test measures hamstring flexibility via a dynamic straight leg raise while the individual is supine. Limitations to H-test include a lack of functionality, because it does not replicate the demands of most sports.

In our opinion, an athlete’s successful return-to-play also involves optimization of muscle balance, postural function, neuromuscular control, and movement patterns. Reassessment of the symptomatic side includes objective findings such as 5 of 5 manual muscle testing (hip extension, knee flexion, hip abduction, hip flexion), improvement in hamstring flexibility, two-joint hip flexion, and gastrocnemius soleus length compared with the initial examination and the non-involved side (52,54). No symptoms should be experienced with the mentioned provocation tests. Once the individual has met the criteria in all domains, a progressive multiplanar running program is started followed by sport-specific drills, noncontact play, noncompetitive sport, and ultimately return to competitive play.

Prevention

With the onset of PHT symptoms, athletes often think, “How could I have prevented this from happening… What could I have done better in preparation or in the moment to avoid injury?” As clinicians, we know prevention goes farther beyond the onset of PHT symptoms. The key to prevention is in early detection of symptoms or dysfunction and better preparation for sport (11). The foundation of movement needs to be present in terms of mobility, flexibility, strength, neuromuscular control, and endurance for a specific sport. The ability to identify and correct abnormal movement patterns (16,17) will have a significant impact on athletic performance (54).

The role of fatigue in increasing risk for PHT is not well elucidated. It is theorized that fatigue can result in biomechanical inefficiency and an increased risk for tendinopathy but there is limited evidence in PHT. Exposure remains the main risk factor and load volume should be monitored closely. To ensure consistent loading parameters, it is important to provide consistent feedback for proper mechanics throughout practice and training programs (62).

Utilization of specific screen tools can help to identify movement asymmetries that can lead an athlete down the path of potential injury. The Functional Movement Screen (FMS) is a test of seven movement patterns that screen an athlete for faulty or asymmetric movement mechanics due to core weakness, lack of stability, lack of flexibility, or poor body mechanics (17). The FMS can be informative in identifying areas where short-term corrective exercise may be helpful, but there is mixed evidence on whether the FMS can predict or prevent injury (69). The role of screens and assessments in sports performance and injury prevention is controversial and deserving of a dedicated review. The Star-Excursion Balance Test may be used to assess lower-extremity stability (52,54).

Overall, there is limited data on prevention of PHT. Peters et al. (59) performed a systematic review of tendinopathy prevention specifically and found only 10 studies which had little to no clear evidence of prevention strategies for tendinopathy and no studies looked at PHT. Lower-extremity injury prevention programs, such as the FIFA 11+ training program (33) and others, have shown consistent results in overall injury prevention but it is unknown if this is specific to PHT. Studies by van der Horst et al. (73) and Petersen et al. (60) looking at more than 1200 soccer players found that eccentric exercise reduced the incidence of hamstring injury in general. More primary and secondary prevention research is needed looking at the dosing and type of eccentric exercise program to reduce PHT. In our experience, the rehabilitation program may need to be performed daily or every other day, but maintenance of progress postrehabilitation may only require performing the home exercise program twice per week.

Interventional Treatments for PHT

Therapeutic modalities and procedural interventions are often used to facilitate the rehabilitation program. These interventions are only necessary for lack of progress or functional regression. Extracorporeal shockwave therapy (ESWT) has been used to treat PHT although there is limited evidence to date on its efficacy and mechanism of action. Cacchio et al. (14) conducted a study in which 40 athletes were divided into two treatment groups receiving either ESWT or traditional conservative treatment (TCT). After 3 months, there were significant pain differences in the two groups (ESWT, 85% successful reduction vs TCT, 10% successful reduction), lending support for further investigation of ESWT in PHT.

The role of peritendinous corticosteroid injections in treating PHT is controversial as the use of local anti-inflammatories for a degenerative process has been brought into question. Ultrasound-guided injections of corticosteroid are safe and effective in reducing pain short term (by theoretically decreasing inflammation in the paratenon or blocking nociceptors in the damaged tendon), but there is a high recurrence rate when used in isolation (55,78).

The use of autologous blood injections, such as platelet-rich plasma (PRP) for tendon problems, has increased in recent years. PRP is defined as autologous blood containing a higher than physiologic concentration of platelets, and it is important to remember that no two samples of PRP are identical (48). Several of the recent systematic reviews (5,29) investigating leukocyte-rich PRP have no data on proximal hamstring tendon. Cook (19) makes the case that in the context of the pathological processes across the continuum of tendinopathy, there is little role for the addition of growth stimulants and additional cells. There is some limited evidence supporting the use of PRP specifically in PHT (see Table 1), but overall, more research is needed, with well-documented injectate composition (51), to better understand the role of autologous blood injections in PHT. Reliable large randomized-controlled trials regarding PRP injections for hamstring tendinopathy are lacking. Our institutional experience regarding PRP hamstring injections (24,63) has found significant improvement in Hip Outcome Scores for activities of daily living and sport-specific function and the International Hip Outcome Tool.

Table 1
Table 1:
Summary of PRP studies for PHT.

Percutaneous needle tenotomy (37,38) has been used for PHT with significant reduction in pain symptoms although the studies are limited in scope and design. Other interventions including percutaneous ultrasonic tenotomy, high-volume injection (58), and percutaneous needle scraping (2) have shown favorable outcomes for recalcitrant tendinopathy although no study has looked at PHT specifically which poses unique challenges due to the depth of the tendons and proximity to the sciatic nerve. There is currently insufficient evidence to support the use of these treatments for PHT.

Surgery

The overwhelming majority of proximal hamstring tendon and muscle injuries respond well to nonoperative treatment but it is important to recognize surgical indications, such as acute avulsion or retraction hamstring injuries and possibly for chronic recalcitrant tendinopathy. This review focuses on tendinopathy, and therefore, acute injuries, such as partial or full thickness strains, are not covered in depth. However, a strain may precede or follow tendinopathy, and one should be familiar with surgical considerations. Wood et al. (77) reviewed 72 surgical cases of proximal hamstring tendon avulsion and found 80% of the cases returned to the preinjury level of activity, including all seven professional athletes, similar to earlier work by Folsom and Larson (30) who reported a 76% return to preinjury level. With complete avulsion and hamstring retraction, a delay in surgical repair renders the repair more technically challenging, may increase the likelihood of sciatic nerve involvement, and overall worsens functional outcome (77), although there is no evidence-based timeframe delineation. Surgery may be considered in isolated conjoint tendon avulsion in active patients and elite athletes or when two of the three hamstring tendons are ruptured at the ischial tuberosity. There is limited evidence regarding surgical consideration when there is complete avulsion of only one tendon, and all nonsurgical options should be explored in decision making.

The second instance in which surgery may be considered is with chronic PHT that has poorly responded to comprehensive conservative management. Lempainen et al. (44) reviewed 103 cases and reported an 89% rate of return to sports activity by 12 months after surgery (semimembranosus tenotomy and attachment to the biceps femoris +/− sciatic nerve exploration) for PHT. Benazzo et al. (8) conducted an 11-yr follow-up of 17 high-level athletes who underwent surgery for PHT and reported all returned to preinjury level of activity within 5 months with no complications. Overall, surgery is an option but must be weighed cautiously with consideration for the preinjury level, chronicity of injury, prior treatment, and most importantly the proper diagnosis and pathoanatomy.

Conclusions

Successful rehabilitation of PHT is certainly a challenging clinical condition to recognize and treat. Often, patients have had at least one or two prior opinions or diagnoses before receiving an accurate and specific diagnosis of PHT that explains their symptoms and functional limitations. Early diagnosis is helpful. Early education for the patient who is often an avid and healthy middle-aged athlete also is prudent. In general, the rehabilitation outcome and return to activity is successful most of the time without the need for medications, injections, or surgical treatment. The keys to successful rehabilitation are teaching the patient or athlete how to modify tendon load, notably ways to gradually increase load through progressive resistive exercises, including eccentric training, to relieve pain and restore function to the proximal hamstring. Second, identifying and correcting inefficient movement patterns, improving muscle balance, and avoiding overstretching are recommended. Maximizing the rehabilitation outcomes requires a compliant and educated patient who has been equipped with an individualized home exercise program that addresses progressive loading and biomechanical exercises as discussed. There is no evidence now that we can prevent reoccurrence of PHT, and further research is needed to elucidate risk factors, prevention, and reinjury of PHT.

The authors declare no conflict of interest and do not have any financial disclosures.

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