Hip, Pelvis, and Thigh Injuries in Runners

Introduction and Terminology

Use of the term “strain” in reference to muscle injuries has been debated due to lack of specificity and a universally accepted definition. The 2012 Munich consensus statement on muscle injuries in sport recommended substituting “tear” for structural injuries of muscle. In practice, however, “strain” remains in common usage. Some authors advocate continuing to use “strain” to refer specifically to noncontact muscle injuries. Others use the more general term “injury” of muscle. Here, we will use strain to refer to noncontact acute muscle injuries. Regardless of the term used to describe them, sports-related muscle injuries are common. The specific incidence of hamstring, quadriceps, hip adductor, and hip flexor strains in runners other than sprinters and other short-distance track athletes, however, is not well characterized and also depends on the specific definition used. Hamstring strains are the most common thigh muscle strain. Thigh muscle strains occur more commonly in sports that involve regular sprinting, jumping, rapid running speed changes and/or rapid changes in direction, particularly soccer, football, and in short-distance track-and-field events; however, thigh muscle strains also occur in distance runners. In a study of hamstring strains in elite track-and-field athletes, 8% of injuries occurred in middle- and long-distance runners. The most robust data regarding the incidence of thigh muscle injuries in runners are from the NCAA injury database. Table 17.2 summarizes the incidence of hamstring, quadriceps, hip flexor, and hip adductor strains in track and cross-country athletes from NCAA data across the 2009–10 through 2013–14 school years.

Muscle Injury Classification

In addition to controversy over the terminology of acute muscle and tendon injuries, there is no universally accepted definition, classification, or grading system for muscle strains. The 2012 Munich consensus statement recommended separating indirect/noncontact muscle injuries as listed in Table 17.3 , with indirect/noncontact muscle injuries separated into overexertion-related disorders, neuromuscular muscle disorders, and partial and total/near-total tears. Partial muscle tears were further divided into minor and moderate, based on clinical presentation and imaging findings.

In 2014, the British Athletics Muscle Injury Classification was proposed as listed in Table 17.4 .

Presentation and Risk Factors

Acute thigh muscle strains, particularly structural injuries with findings evident on MRI or ultrasound, often occur during muscle contraction or with overstretching. With hamstring strains in particular, two patterns have been described: strains associated with high-speed running and overstretching injuries. Overstretching-type hamstring injuries do not typically occur during running. Runners who do speed work or weight lifting in addition to long-distance running may be more prone to thigh muscle strains due to the forceful contractions associated with those activities; however, there may also be a protective effect of maintaining balanced strength and flexibility across the muscle groups of the thigh. The typical presentation of a structural muscle injury is sudden thigh pain during athletic activity, although pain may not develop until after activity or the following day with more mild injuries. In more severe injuries, bruising and localized swelling may develop, weight-bearing may be difficult, and a palpable muscle or tendon defect may be present. Strains are more common in muscles that cross two joints and are therefore more common in the rectus femoris than other quadriceps muscles. Strains in the hamstrings most frequently involve the biceps femoris. Hamstring strains in particular tend to occur during the terminal swing phase of high-speed running with the hamstrings commonly understood to be eccentrically controlling deceleration before foot strike ; however, it has been suggested that the hamstrings' contraction during swing phase may actually be isometric rather than eccentric. Muscle strains can occur anywhere in the muscle but are particularly prevalent surrounding the myotendinous junction. Strains involving the intramuscular portion of the rectus femoris and hamstring tendons are also common and may take longer to heal resulting in prolonged return to sport. Injuries occurring proximally are also associated with more prolonged recovery. Fatigued muscle has been shown to be more susceptible to strain in the laboratory setting. To our knowledge, there is no study specifically examining intrinsic risk factors for first-time thigh muscle strain in runners. In soccer athletes, risk factors for muscle strain have been shown to include recent similar injury (with or without full clinical recovery prior to return to sport), asymmetry of quadriceps and hamstring flexibility and eccentric strength, heavier athlete weight, and shorter stature.

Diagnosis/Diagnostics

The initial diagnosis of thigh muscle strain is typically clinical, but musculoskeletal ultrasound and MRI can help in determining injury severity and prognosis and guiding return to play. The role of x-rays is the exclusion of other pathology, particularly avulsion fracture in the presence of pain localizing to a tendon origin or insertion. Avulsion of the anterior inferior iliac spine (AIIS) at the origin of the rectus femoris is a common injury in the skeletally immature and can present with thigh pain, typically occurring from forcefully kicking a ball or during sprinting or jumping. Table 17.5 details AIIS and other pelvic apophyseal avulsion injuries and the timing of appearance and closure of pelvis apophyses. With hamstring injuries in particular, the potential role of x-rays is to exclude avulsion at the hamstring origin on the ischium. In general, separating thigh muscle strains into those with and without MRI or ultrasound findings is a useful distinction since injuries with such findings have been shown to be associated with a longer recovery time in comparison to injuries with normal imaging. This is particularly true with hamstring strains. MRI or ultrasound evaluation should be considered in all suspected structural muscle injuries (type 3 and 4 injuries in the Munich classification system). Advanced imaging allows better injury prognostication and evaluation for associated tendon involvement.

Management/Rehab and Return to Running

Mild thigh muscle strains often heal quickly, with data from NCAA athletes demonstrating that most injuries involve no to minimal time loss from sport, but some may require a prolonged period of recovery before return to sport. Recovery in runners rarely exceeds 6 weeks. Time to return to sport has been shown to be longer in injuries with muscle fiber disruption on MRI or ultrasound. Other factors associated with a longer recovery time from hamstring strains include overstretching as the injury mechanism, greater loss of knee range of motion, time to initial medical evaluation more than 1 week, and increased pain on a visual analog scale. The management of mild thigh muscle strain involves rest from athletic activity as needed, ice, compression, and elevation if swelling is present. More severe injuries leading to a significantly antalgic gait may require a period of protected weight-bearing with crutches. Earlier return to running risks prolonging recovery and symptom duration as well as an increased risk of recurrent injury at the same location. The risk of recurrent muscle strain remains elevated for a prolonged period following return to sports, and athletes should be appropriately counseled about that risk. In data from athletes in various sports, factors associated with risk of recurrent hamstring injury have been shown to include higher number of previous hamstring injuries, lacking full knee extension, pain with resisted knee flexion, decreased range of motion with active knee flexion, and tenderness to palpation over the hamstring muscles at the time of return to athletic activity. Monitoring muscle changes via musculoskeletal ultrasound can help to guide the timing of return to play, particularly by allowing serial evaluation of muscle strains that are not fully healed despite resolution of symptoms. Physical therapy can help to promote return to baseline strength and flexibility and to address any underlying asymmetry in strength and flexibility as well as deficits in neuromuscular control. Typical rehabilitation protocols involve a period of rest followed by the initiation of stretching exercises and concentric before eccentric strengthening exercises. Progression is then made to sport-specific exercises and drills and return to running. Platelet-rich plasma (PRP) has been evaluated in acute lower limb muscle injuries but results have been mixed ; however, its potential benefit continues to be debated.

Introduction, pathophysiology, and risk factors

Albeit less common than muscle strains of the hamstring, proximal hamstring tendinopathy (PHT) is a significant cause of posterior thigh and buttock pain in the runner. PHT occurs on a spectrum, with peritendinous edema, tendinosis, and degenerative partial tears frequently occurring. In a case series of PHT treated surgically, tendinosis was identified as the underlying pathology in all cases with no inflammatory cells identified to suggest an inflammatory etiology. Any or all of the proximal hamstring tendons can be affected.

Running is the sporting activity most often associated with the development of PHT. Middle- and long-distance runners are particularly affected. As with other painful overuse tendon disorders, PHT occurs at the nexus of patient-specific intrinsic and extrinsic factors. Additional reported risk factors include activities that involve repetitive squatting and lunging, changes to training regimen, prior injury, fatigue, age, anterior pelvic tilt, muscular imbalances including reduced gluteus maximus activity resulting in hamstring overload for hip extension, and limited quadriceps flexibility.

Presentation and exam

PHT presents with chronic, insidious, often progressive pain at the ischial tuberosity and buttocks. Pain can also radiate to the posterior thigh and popliteal fossa, mimicking a radicular pattern of pain. Irritation of the sciatic nerve has been reported, thought to be related to entrapment from adhesions and scar or by dynamic entrapment of the nerve by a thickened tendon during the swing phase of the running cycle. Symptoms are exacerbated with loading of the tendon, which occurs repetitively with hip extension and knee flexion during running. As tendinopathy progresses, symptoms can occur with less provocation and with sitting. Over time, runners may report reduced performance and progressive pain at shorter distances. Evaluation of potential risk factors should include discussion of the training regimen and any previous injuries or similar pain.

Tenderness to palpation is typically present over the proximal hamstring tendons and/or the ischial tuberosity. Resisted knee flexion and hip extension and passive hamstring stretching can provoke pain; however, strength and flexibility are often preserved or only slightly reduced. Furthermore, a detailed evaluation of adjacent structures (lumbosacral spine, sacroiliac joint, etc.), neurologic examination, and assessment of the kinetic chain are important in the search for alternative diagnoses and contributing factors. Three provocative tests have been described for PHT. The Puranen-Orava test is performed with the patient standing, hip flexed to 90 degrees, knee fully extended, and the foot supported. To perform the bent-knee stretch test, the subject is supine while the knee and hip are maximally flexed and the knee is slowly extended. The modified bent-knee stretch is performed with the subject supine; the knee and hip are maximally flexed and the knee is rapidly extended. Each test has demonstrated high inter- and intra-examiner reliability and moderate to high sensitivity, specificity, and both positive and negative predictive values. The modified bent-knee stretch test performed the best of the three tests, with a sensitivity of 89%, specificity of 91%, and positive likelihood ratio of 10.2.

Imaging

Imaging is helpful to solidify the diagnosis of PHT, particularly in refractory or uncertain cases, as well as to assess for other competing diagnoses. X-rays are often unrevealing. MRI and ultrasound are the most useful imaging modalities for PHT, with MRI being the most sensitive. Tendon thickening, tendon signal change, peritendinous edema, and edema within the ischium are characteristic findings on MRI (see Fig. 17.1 ). Ultrasound may also show tendon thickening, hypoechoic foci within the tendon, heterogeneous echotexture, intratendinous calcifications, peritendinous edema, and ischial tuberosity cortical irregularity. Imaging findings of PHT can also be present in asymptomatic individuals.

Management

The conservative treatment for PHT includes activity modification, patient education, and physical therapy to progressively load the tendon and address biomechanical contributors. There is a paucity of high level evidence, however, to clarify many of the variables of rehabilitation for PHT. Eccentric exercises have shown benefit in chronic tendinopathy and are often used in the management of PHT. Common eccentric hamstring exercises include Nordic hamstring curls, deadlifts, and split squats. Eccentric exercises are generally incorporated once isometric and concentric exercises are well tolerated. Running gait evaluation and retraining and a stepwise return to running program are important capstones to the management of PHT. Expert opinion supports running retraining in the management of PHT, although no specific studies exist evaluating this specific recommendation. Recommendations for running gait alterations generally include reducing anterior pelvic tilt, overstriding, and force of impact, as well as increasing cadence and hip/knee flexion during swing phase.

Interventional treatments for PHT are considered when more conservative treatments have not been effective. There is limited high-quality evidence to guide these treatments. In a randomized control trial, shockwave therapy appeared to be safe and more effective than traditional conservative treatment. Corticosteroid injections for PHT can improve pain in the short term; however, recurrence of pain is common. Corticosteroid injections for chronic tendinopathy should be considered carefully and with an understanding of the degenerative rather than inflammatory nature of tendinopathy. The use of PRP and tenotomy has recently increased; however, minimal published evidence is specific to PHT. Fader et al. retrospectively analyzed 18 patients with PHT treated with a single PRP injection under ultrasound guidance and reported 80% of patients experienced greater than 80% improvement of pain. Imaging guidance, typically ultrasound, should be used to ensure safe and accurate needle placement. The vast majority of PHT cases can be managed nonoperatively, and surgery should be considered cautiously only in chronic, refractory cases or for those when sciatic nerve pathology is present. Surgery for PHT usually consists of open tenotomy with possible lysis of adhesions around the sciatic nerve, with most athletes returning to their prior level of sports participation.