The popularity of running among young athletes has significantly increased over the past few decades. As the number of children who participate in running increases, so do the potential number of injuries to this group. Proper care of these athletes includes a thorough understanding of the unique physiology of the skeletally immature athlete and common injuries in this age group. Treatment should focus on athlete education, modification of training schedule, and correction of biomechanical deficits contributing to injury. Early identification and correction of these factors will allow a safe return to running sports.
Key points
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Youth and adolescent running injuries are becoming more common as more children participate in running as a sport.
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Injuries to the youth athlete differ from those in adults because of growth-related issues.
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Early detection of injuries and correction of contributing factors can help prevent injury.
Introduction
Whether for exercise or sport, the popularity of running has greatly increased over the past few decades among all individuals, including children. In 2007, an estimated 12 million children aged 6 to 17 years participated in some form of running for exercise. A 2012 study of United States youth ages 12 to 15 years showed that outside of school-based gym classes, running was the second most common activity among boys (33.5%) behind basketball and the most common activity among girls (34.9%). In 2014, the National Federation of High Schools High School Participation Survey of all 51 state cross-country and track and field associations noted that a total of 1,059,206 athletes participated in track and field (580,321 boys, 478,885 girls) and 470,668 athletes participated in cross-country (252,547 boys, 218,121 girls) during the 2013/2014 season. Several factors have contributed to running’s increased popularity, including the development of competitive running programs at the middle and high school levels and a 2008 initiative by the United States Government to increase physical activity in youths to combat obesity. As the number of children who participate in running increases, however, so does the potential number of injuries. This article reviews the epidemiology of running injuries in youth and the unique physiology of the skeletally immature athlete, and discusses common injuries and treatment strategies for the youth running athlete.
Introduction
Whether for exercise or sport, the popularity of running has greatly increased over the past few decades among all individuals, including children. In 2007, an estimated 12 million children aged 6 to 17 years participated in some form of running for exercise. A 2012 study of United States youth ages 12 to 15 years showed that outside of school-based gym classes, running was the second most common activity among boys (33.5%) behind basketball and the most common activity among girls (34.9%). In 2014, the National Federation of High Schools High School Participation Survey of all 51 state cross-country and track and field associations noted that a total of 1,059,206 athletes participated in track and field (580,321 boys, 478,885 girls) and 470,668 athletes participated in cross-country (252,547 boys, 218,121 girls) during the 2013/2014 season. Several factors have contributed to running’s increased popularity, including the development of competitive running programs at the middle and high school levels and a 2008 initiative by the United States Government to increase physical activity in youths to combat obesity. As the number of children who participate in running increases, however, so does the potential number of injuries. This article reviews the epidemiology of running injuries in youth and the unique physiology of the skeletally immature athlete, and discusses common injuries and treatment strategies for the youth running athlete.
Epidemiology
Whereas the epidemiology of running-related injuries in adults is well studied, there is limited information regarding the epidemiology of running-related injuries in children. Mehl and colleagues found that between 1994 and 2007 a total of 225,344 children (boys and girls roughly equal) were treated in United States Emergency Departments for running-related injuries. Over this period, there was an annual increase in incidence of 34%, with age 12 to 14 years having the highest injury rate (45.8 per 100,000 persons). Nelson and colleagues reviewed Emergency Department encounters for injuries to children sustained in physical education class between 1997 and 2007. A total of 405,305 injuries were sustained in 5- to 18-year-olds during this period. Of these encounters, more than 50% could be attributed to activities involving running (running 25.1%, basketball 20.3%, football 7.8%). Similar to the Mehl study, the annual rate of all injury increased over the study period. Though not specific to running, younger children are more likely to have traumatic injuries and fractures in comparison with older children and adolescents, who are more likely to develop overuse injuries.
Studies focused on high school cross-country athletes and their injuries have revealed several interesting findings. A prospective study by Rauh and colleagues of 421 runners over one season found that 38.5% sustained at least one injury (defined as any reported muscle, joint, or bone problem/injury of the back or lower extremity resulting from running in a practice or meet). Girls were noted to have sustained a significantly higher overall injury rate (19.6 per 1000 athletic events [AEs]) than boys (15.0 per 1000 AEs). For girls, important predictors of injury were sustaining an injury during the summer before the season and quadriceps angle greater than 20°. Important predictors of injury for boys included a history of multiple running injuries and quadriceps angle greater than 15°. A follow-up study by Rauh assessing summer training factors noted that runners who did not frequently alternate short and long mileage days ( P = .01), ran for 8 weeks or less ( P = .31), and ran a higher percentage predominately on hills ( P = .001) or irregular terrains ( P = .004) were more likely to be injured during the season. A retrospective study of high school runners (442 females and 306 males) by Tenforde and colleagues noted that more than 68% of females and 59% of males reported a previous injury. Higher weekly mileage was associated with previous injuries in boys ( P = .05) but not girls. In 2013, Tenforde and colleagues reported a prospective evaluation of risk factors for stress fractures in 748 competitive high school runners (442 girls and 326 boys), and identified stress fractures in 5.4% of girls and 4.0% of boys. Tibial stress fractures were most common in girls, and the metatarsal bone was most frequently fractured in boys. These studies highlight the need to further understand the unique aspects of the child athlete and common injuries they sustain while running.
Unique considerations for the growing athlete
Children have varying rates of growth and development that are influenced by hormonal, genetic, and environmental factors. Because children are skeletally immature, they are at particular risk for injury at the growth plates (physis), tendon attachment sites (apophysis), and articular cartilage at joint surfaces. The growth plate is especially vulnerable and depends on a variety of hormonal stimuli, including growth hormone (GH), insulin-like growth factor I (IGF-I), sex steroids, thyroid hormones, paracrine growth factors, and cytokines. In addition, variable rate of growth in the maturing athlete has a significant influence on biomechanics, which further puts them at risk for injury. This discussion focuses on key areas in the maturing athlete that may affect running injuries.
Bone Mineral Content
Adolescence is a period when individuals gain approximately half of their adult bone mineral content; however, the rate of bone deposition sharply declines after the age of 16 to 18 years. Both men and women reach peak bone mass early in the third decade of life. Of interest, some cross-sectional evidence has shown that adolescent runners have an elevated prevalence of low bone mass and decreased bone mineral accumulation with respect to expected values. Although a full discussion is beyond the scope of this article, the female athlete triad, which is well described in adolescent runners, is one of the most well studied factors affecting adolescent bone development. The triad is currently understood to involve relationships between energy availability, menstrual function, and bone health. In addition, new research suggests that young male athletes may exhibit processes similar to the female athlete triad, also associated with increased risk of impaired bone mineral development. In general, low energy availability seems to be a key component of bone health during development.
Endocrine
Three main endocrine axes affect growth and development during adolescence: the hypothalamic-pituitary-adrenal axis, the GH axis, and the hypothalamic-pituitary-gonadal (HPG) axis. The GH axis is largely responsible for the rapid adolescent height spurt by exerting its effect through a set of insulin-like growth factors, interaction with sex steroids, and stimulation of local IGF-I in cartilage and bone directly. The HPG axis generally plays a larger role in skeletal maturity and bone mineralization through interactions between energy balance, sex hormones, and proper bone development. Estrogen has been found to play a major role in skeletal maturity through effects on bone and cartilage in both girls and boys. Increasing estradiol concentrations correlate with pubertal growth spurts and peak height velocity, and contribute to epiphyseal closure through multiple mechanisms, but primarily by stimulating chondrogenesis in the epiphyseal growth plate. Androgen receptors are found in developing and mature osteoblasts, and are likely responsible for the greater increase in periosteal bone deposition and bone strength in men compared with women.
Peak Height Velocity
Peak height velocity is a measure of the rate of growth speed in height. Although this can vary regionally and depends on a variety of factors, on average girls will reach their peak height velocity at 12 years of age and boys at 14 years. It has been shown that growth in children is not uniform and that maximum growth speed in the legs occurs before maximal sitting height.
Peak height velocity corresponds to important physiologic changes that are important to consider. First, bone mineral density is at its lowest level just before peak height velocity. Therefore, bones are at their weakest during this period of significant growth. In addition, cartilage that is growing to accommodate the increase in size of joints with growth is weaker than mature cartilage. The long bones also tend to lengthen before the muscle-tendon complex, creating a tension in the muscle during periods of rapid growth. Such changes put a great deal of strain on thinning growth plates and apophyses. These events highlight the importance of understanding the biological versus chronologic age of the youth runner, and the need for further research regarding appropriate training parameters for a specific athlete.
Common running injuries
Apophyseal Injuries
Apophyseal injuries are frequently encountered in the skeletally immature runner. The apophysis represents a secondary ossification center where a tendon attaches to the bone. During period of peak growth velocity, the long bones grow in length faster than the myotendinous unit, resulting in injury to the apophysis with overtraining. Apophyseal injuries can be divided into 2 categories: apophysitis (secondary to overtraining, as in distance running) or avulsion-type injuries (seen in sports requiring sudden starting and stopping, such as sprinting or soccer) ( Fig. 1 ). Although any apophysis is at risk for injury, common areas in the youth runner include the pelvis (ischial tuberosity, anterior superior and anterior inferior iliac spine), the knee (Osgood-Schlatter disease, Sinding-Larsen-Johansson lesion), the heel (Sever disease), and the fifth metatarsal (Iselin disease).
Athletes will typically present with pain in the apophyseal region based on the location of the injury and an inability to continue running. Understanding the mechanism of injury and tendon attachments can help with diagnosis. Physical examination including palpation of the injured area, and passive stretch or activation of the involved muscle/tendon producing pain will confirm the diagnosis. Radiographs should be ordered to confirm a suspected avulsion fracture. Fortunately, most of these injuries will respond to a comprehensive multidisciplinary conservative treatment program. Rehabilitation should focus on an appropriate period of rest, use of modalities, activity modification, correction of biomechanical deficits (inflexibility or weakness), nutritional assessment, and correction of training errors that contribute to the injury. Surgery and immobilization is rarely needed and is most often used in cases of significantly displaced avulsion fractures. Further details of the most common running-associated apophyseal injuries in children are outlined in Table 1 .
| Apophyseal Injury Type | Anatomy | Epidemiology Notes | Mechanism of Injury | History/Examination Findings | Management | Other Considerations |
|---|---|---|---|---|---|---|
| Ischial tuberosity | Origin of long head of biceps femoris, semitendinosus, and semimembranosus muscle | Most common site of pelvic apophyseal injury | Flexion of the hip with the knee extended, repetitive knee flexion, and repetitive eccentric contraction of the hamstring muscles | Posterior thigh pain and tenderness, popping sensation, and localized swelling |
| May be associated with sciatic nerve injuries |
| Anterior superior iliac spine | Origin of the sartorius and TFL | Second most common site of pelvic apophyseal injury | Contraction of the sartorius, which acts to flex the hip and knee, and the TFL, which assists with abduction and lateral rotation of hip | Similar to AIIS apophyseal injury | See ischial tuberosity management above | May cause meralgia paresthetica by compression of the lateral femoral cutaneous nerve |
| Anterior inferior iliac spine | Origin of the 2 heads of the rectus femoris muscle | Third most common site of pelvic apophyseal injury | Extension of the hip and knee flexion | Findings similar to those of ischial tuberosity but at the anterior thigh | See ischial tuberosity management above | — |
| Osgood-Schlatter disease | Patella tendon insertion at the tibia tubercle | Most commonly seen in boys 12–15 y old and girls 8–12 y old | Extension of the knee | Insidious onset of pain localized to the anterior tibial tubercle worse with running and jumping that may be associated with a palpable mass at the site | Conservative management including ice massage, oral anti-inflammatories, and protective knee padding (if kneeling regularly). Physical therapy to strengthen muscles; crossing the knee may be helpful Refractory cases with persistent symptoms may be managed surgically with drilling or excision of the tubercular mass; this is only considered after skeletal maturity | Can result in premature closure of the anterior tibial epiphysis resulting in genu recurvatum |
| Sinding-Larsen-Johansson lesion | Patella tendon origin at the inferior pole of the patella | — | Similar to Osgood-Schlatter | Insidious onset of pain localized to the inferior pole of the patella, worse with running and jumping | A conservative approach similar to Osgood-Schlatter disease. Surgery is generally not considered even in the skeletally mature | — |
| Sever disease (calcaneal apophysitis) | Insertion of the Achilles tendon | Boys more commonly affected than girls. Most commonly present early in the sports season | Ankle dorsiflexion | Insidious onset of posterior heel pain. Rarely associated with swelling. Bilateral findings are common. Pain is elicited with compression of the medial and lateral heel | Conservative management including ice, relative rest, a limited trial of oral anti-inflammatories, physical therapy to stretch ankle plantarflexors and strengthen ankle dorsiflexors, and the use of heel cup orthotics. No surgical procedures are used commonly in the management of Sever disease | — |
| Iselin disease (fifth metatarsal head apophysitis) | Insertion of the fibularis brevis and tertius muscles | Generally thought to be rare, although true prevalence underestimated because of misdiagnosis. Most commonly seen in 10-y-old girls and 12-y-old boys | Ankle eversion, subtalar protonation, and forefoot abduction | Lateral foot pain worse with wearing shoes and weight-bearing activity. May have a tender prominence of the base of the fifth metatarsal | Conservative management including ice, relative activity restriction, appropriate footwear, and limiting running on surfaces that require foot stabilization in the coronal plane. Refractory cases may be managed with 2–3 wk in a CAM boot | — |
Lower Extremity Tendon Injuries
Lower extremity tendon injuries are more common than apophyseal injuries in the skeletally immature runner. Similarly to the adult runner, they are often due to overtraining in the setting of biomechanics deficits involving flexibility or strength. The most common sites of injury involve the patellar tendon, Achilles tendon, or posterior tibialis tendon ( Table 2 ). Similarly to apophyseal injuries, tendons can be injured during periods of peak growth velocity. Early on in the clinical course, pain may occur only after athletic activities, but as the disease progresses pain may be present throughout the entirety of sporting activities or even when not participating in sports. The most consistent physical examination findings are localized tenderness on the specific tendon and flexibility or strength deficits. Most tendon injuries can be treated without imaging, although ultrasonography may be used to identify any significant injury.
| Involved Tendon | Anatomy | Epidemiology Notes | Mechanism of Injury/Imaging Findings | History/Examination Findings | Management |
|---|---|---|---|---|---|
| Patellar tendon | Tendon stretches from the apex of the patella, distally to the tibial tuberosity; this tissue is a continuation of the quadriceps tendon | Prevalent in jumping athletes, but also affects runners | Chronic degenerative process Ultrasound imaging demonstrates abnormal tendon with localized tendon widening at the point of tenderness associated with hypoechoic areas and occasional neovascularization | May have a history positive for increased activity, but pain is typically insidious without a history of direct trauma Activity-related anterior knee pain, with focal tenderness at the inferior pole of the patella; pain is exacerbated by knee flexion and prolonged activity Early clinical course may present with pain after athletic activities only, but later pain may be present throughout entirety of sporting activities or even when not participating in sports The most consistent physical examination finding is localized tenderness at the inferior pole of the patella; the most specific physical examination finding is pain with a decline squat test | Aggressive nonoperative management is essential and may include activity modifications Treatments include ice and analgesic creams, oral medications, bracing, and physical therapy that include stretching and eccentric strengthening Eccentric muscle training is a mainstay in conservative treatment Eccentric strength training shown to be effective in reducing pain associated with neovascularization Some research has shown eccentric decline squat training to be superior to standard eccentric squat training Recalcitrant cases may require further intervention using ultrasound-guided injection of biological agents, or surgical tenotomy |
| Achilles tendon | Tendon stretches from the plantaris, gastrocnemius, and soleus muscles distally to the calcaneus | Strongest tendon in the body Midsubstance tendinopathy (55%–65%) is more common than tendinopathy at the insertional site at the calcaneus (20%–25%) Most commonly affects athletes in running or jumping sports | Chronic degenerative process Diagnosed clinically, but ultrasound and MRI may be useful when diagnosis is unclear or when a partial tear needs to be ruled out | May complain of pain or stiffness in the Achilles 2–6 cm above the calcaneal insertion; pain is worse with activity Tenderness positive in the body of the tendon or directly over the calcaneal insertion, with or without crepitus | Eccentric calf exercises have the greatest evidence and best outcomes for treatment of midsubstance Achilles tendinopathy Recalcitrant cases may require further interventions using ultrasound-guided injection of biological agents, or surgical tenotomy |
| Posterior tibialis | Tendon stretches from medial border of tibia to insertion on tuberosity of the navicular | Commonly overloaded from excessive pronation, especially while running | Chronic degenerative process Diagnosed clinically, but ultrasound and MRI may be useful when diagnosis is unclear or when a partial tear needs to be ruled out | May complain of pain along the medial aspect of the ankle Tenderness positive in along the tendon near the medial malleolus | Nonoperative management is essential and may include activity modifications Treatments include ice, oral medications, physical therapy, and orthotics |
Aggressive nonoperative management is essential and may include a variety of modalities. Most treatment plans involve a combination of activity modifications, topical treatments including ice and analgesic creams, oral medications, bracing, and physical therapy that includes stretching and eccentric strengthening. Eccentric muscle training is a mainstay in the conservative treatment of many tendinopathies, and studies have shown eccentric strength training to be effective in reducing pain associated with neovascularization. Though uncommon, recalcitrant cases may require further interventions using ultrasound-guided injection of biologics or tenotomy. However, these treatments have not been studied in the child/adolescent athlete, limiting their use on the basis of evidence-based practice.
Bone
Medial tibial stress syndrome and stress fracture
Medial tibial stress syndrome (MTSS) and stress fracture are the most common causes of bone injury in runners, including skeletally immature athletes. Both MTSS and stress fractures are covered in full detail in separate reviews in this issue. Some unique features that differ between the pediatric and adult population are noteworthy.
MTSS affects between 7.2% and 35% of all runners, including the pediatric population. Stress fractures account for 16% of all running injuries, with high school athletes having an incidence similar to that of adults. The exact etiology of MTSS is under debate, but most likely relates to a traction injury from strong leg muscles (soleus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior) causing a periosteal reaction at their insertion. Continued stress will overload the bone, leading to a stress fracture. A recent systematic review by Hamstra-Wright and colleagues showed that only increased body mass index (BMI), a navicular drop, and increase range of motion of ankle dorsiflexion and hip external rotation were consistently shown to increase the risk of MTSS in all age groups. A prospective study of high school cross-country runners to identify modifiable risk factors for MTSS noted that girls were 2.5 times more likely than boys to develop MTSS, and those with higher BMI were also more likely to develop MTSS. Of note, age itself has not been studied as a risk factor for MTSS.
The presentation for children and adults for these entities is similar. Both MTSS and stress fractures of the leg present similarly, and consist of leg pain starting without obvious injury. Classically the two can be differentiated by the fact that MTSS pain may improve with activity, whereas stress-fracture pain tends to worsen with activity. Typically a child presenting with MTSS will complain of running-induced leg pain at the posteromedial aspect of the tibia in the middle or lower third of the leg. A child with a tibial stress fracture may have pain in a similar location, although it may be more focal. Both causes of leg pain can become progressively more persistent, and may even be present at rest is severe cases. Often the symptoms develop after an increase in running intensity, duration, or frequency. Physical examination for both MTSS and stress fractures of the tibia may show tenderness of the tibia with or without mild swelling in the area of tenderness. With this degree of similarity, these entities may be difficult to differentiate using history and examination alone.
The approach to diagnostic imaging is similar in children and adults. However, extra discretion should be exercised when obtaining imaging in children so as to limit lifetime radiation exposure. Plain radiographs are of limited value, as they inconsistently show findings in patients with MTSS and stress fractures. If radiographs are ordered, bilateral views should be considered in the skeletally immature athlete to assess subtle growth plate asymmetries. Bone scintigraphy is of limited use, as there may be increased uptake in areas of active growth and findings are often seen in asymptomatic individuals. MRI can be useful because it avoids exposure of the child to ionizing radiation and can reveal signs of a stress reaction in injured bone, particularly with stress fractures, which are not seen on plain radiographs.
For both entities, conservative management is a mainstay of treatment. Most conservative management centers on the principles of ice, compression, and elevation in addition to progressive rehabilitation programs with a physical therapist and activity modification with reduced weight bearing, deep water running, selective bracing, correction of biomechanical deficits, and, rarely, immobilization. The treatment duration and strategy for individuals with stress fractures varies depending on the location and severity of the stress fracture. The time for healing has been reported to be 6 to 8 weeks in low-risk, low-grade stress fractures, and roughly 130 days on average for high-risk stress fractures of both low and high grade. Children seem to require even longer periods to heal. Delayed diagnosis and mismanagement can lead to a significantly longer time to heal and delay in return to running, and may lead to avascular necrosis, osteoarthritis, and recurrence. This aspect can be particularly important for children, in whom a significant injury to the bone can cause abnormal growth and potentially lead to limb-length disparities.
Osteochondritis dissecans
Juvenile osteochondritis dissecans (JOCD) represents a unique bone injury that may present in the skeletally immature running athlete. The exact etiology of JOCD is not known, although it is widely accepted that repetitive trauma and secondary vascular effects that occur posttraumatically play a central role. Other causes have been considered, including inflammation, ischemia, and heredity. JOCD represents a separation of articular cartilage from the underlying subchondral bone, and can lead to sclerotic or fibrotic changes of the joint and the formation of a loose body. Fortunately, the healing potential in the skeletally immature athlete is better than in the skeletally mature athlete.
The knee is the most commonly affected joint in JOCD, which classically is located on the lateral aspect of the medial femoral condyle, although other areas may be affected and bilateral lesions are present 30% to 40% of the time. Typically presentation is an athletic child with vague knee pain that worsens with activity or a specific traumatic event. Mechanical symptoms of popping, catching, and locking are common, but may be absent before the lesion is partially or fully detached. Physical examination is often nonspecific, with tenderness of the affected condyle with the knee flexed. Knee effusions are uncommon, seen in less than 20% of children with JOCD of the knee.
The talar dome is the next most commonly (though rarely) involved area of JOCD, accounting for 4% of all osteochondral lesions. The medial aspect of the talar dome is more commonly affected, and bilateral lesions are not uncommon (7%–25%). A child presenting with JOCD of the talus will most often complain of generalized ankle pain that may localize medially or laterally depending on the location of the lesion. There may be a history of chronic instability or feeling of joint laxity before the pain. Mechanical symptoms such as clicking or catching with ankle range of motion may be present, but the absence of these symptoms does not rule out JOCD. The physical examination may be notable for tenderness at the anteromedial or anterolateral aspect of the ankle, popping with passive range of motion of the ankle, and possibly an effusion. There are no special tests described in the literature for JOCD of the talus.
The diagnosis of JOCDs requires radiographs and advanced imaging. Plain radiographs of the knee (anteroposterior, lateral, tunnel, and skyline views) or ankle (anteroposterior, mortise, and lateral) should be obtained with particular focus on the common areas of involvement. Although plain radiographs may identify the lesion, MRI is considered the gold standard for evaluation of JOCD and to help determine the stability of the lesion. MRI staging of the OCD ( Table 3 ) will assist in determining nonoperative or operative management. Bone scintigraphy and arthroscopy have been proposed as alternative diagnostic methods. Nuclear scintigraphy does not assist with staging, and arthroscopy may be normal in lesions where the articular cartilage is intact.
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