In the United States an estimated 30 million youth participate in organized sports. The Youth Risk Behavior Survey was a large population-based study performed throughout the 1990s, enabling accurate measurement of the emerging trends in youth sports participation. Results from the 1997 survey reported that 62  % of US high school students participated in one or more sports teams, with most playing in a combination of both school and nonschool teams (Washington, Bernhardt, Gomez, et al., 2001). In addition, many more participate in recreational sports. Injuries are an inherent risk in sports, and approximately 80  % of sports injuries affect the musculoskeletal system. Many patients participate in multiple teams during a given sports season, the rest periods between seasons are short or nonexistent, and there is increasing demand for sporting success from parents, schools, and sporting establishments. In a survey of children and adolescents age 5–17 years, the estimated annual number of injuries resulting from participation in sports and recreational ­activities was 4,379,000 with 1,363,000 classified as serious (requiring hospitalization, surgical treatment, missed school, or a half day or more in bed). Up to 36  % of injuries may be directly related to sports participation in patients in these age groups (Bijur et al., 1995). While the definition of what constitutes a sports injury is varied, some common elements such as need for medical attention, time lost from practice or game, and decreased level of activity are widely used in different definitions. Injuries are commonly grouped into either acute or chronic which are designated macrotrauma and microtrauma, respectively.

One of the most commonly used measures in determining the severity of a sports injury is time lost from participation in the sport. The National Athletic Injury Reporting System (NAIRS) uses the following categories for severity: nonreportable, no time lost; minor, 1–7 days lost; moderate, 8–21 days lost; major, more than 21 days lost; and severe, resulting in permanent disability. Another important documented aspect of sports injuries is incidence of injuries. The two ways in which incidence of injuries are reported are cumulative incidence and incidence of first injury. Cumulative incidence reports the number of injuries sustained by a defined group of athletes. For example, cumulative incidence would record the incidence of injuries of football players over a set period of time. Cumulative incidence is useful because it provides information on an individual athlete’s risk of injury. Incidence of first injury is the risk of any one athlete in a group of being injured.

From incidence studies, it is clear that chronic overuse injuries are far more prevalent than acute sports injuries in those 17 years old and younger. Not only is there a higher incidence of chronic injuries in adolescents but the severity as measured by time lost from sports is also greater. Of all injuries in adolescents, 30–50  % are due to chronic overuse in both sports-related and non-sports-related injuries.

The greatest source of available data on musculoskeletal sports injuries comes from those suffered during interscholastic high school sports. For boys in all sports combined, there is a yearly incidence of injury in high school sports of 27–39  %. Organized sports account for 25–30  % of total injuries, while non-organized sports account for 40  % of total injuries. As one would expect contact sports account for the greatest number of injuries in adolescents. In an 8-year longitudinal study of high school sports, researchers reported that 48  % of athletes sustained at least one injury during their season: 64.5  % of all injuries were minor (no days lost), 30.3  % were mild (1–7 days lost), 3.1  % were moderate (8–21 days lost), and 1.9  % were severe (22 days lost). A study by the American Academy of Pediatrics suggested that female athletes have higher rates of injuries when compared with male athletes (American Academy of Pediatrics: Committee on Sports Medicine and Fitness, 2000). A recent study looking at injury claims from an insurance provider for youth soccer leagues showed that knee and anterior cruciate ligament injuries in female youth soccer players age 12 through 15 were more common than ACL injuries in males of the same age (Shea, Pfeiffer, Wang, Curtin, & Apel, 2004).

Soft tissue injuries such as strains, sprains, and contusions are the most common types of acute injuries. In a national study on sports and recreational injuries, researchers found that 59  % of sprains, 48  % of fractures and dislocations, and 25.5  % of lacerations are caused by sports and recreational activities in those under the age of 18. Furthermore, 36  % of all injuries are from sports. Compared with other injuries, sports did not account for a disproportionate number of serious or repeat injuries. This could serve as an indication to use sports as a model for injuries in adolescents.

There are a number of significant differences between the adult and adolescent musculoskeletal system. The most significant difference between an immature skeleton and the adult skeleton is the presence of growth plates. The growth plate, also known as the physis, is composed of four zones: the resting cartilage or reserve zone, the proliferating cartilage zone, the zone of hypertrophy, and the metaphysis. In bone, there is a diaphysis (middle part of long bone), an epiphysis (end part of long bone), and a metaphysis (between the diaphysis and epiphysis) components. The physis is wedged between the metaphysis and epiphysis. The cartilage of the physis is relatively weak and susceptible to injury, especially during periods of active growth. In particular, the zone of calcification within the physis is the weakest and most commonly injured area; however, fractures confined to this region typically heal without complication.

In adults, the fully grown calcified bone is significantly stronger than ligaments and other soft tissue around the joint. Consequently, in adults, ligaments and soft tissue are more susceptible to injury than bone. In contrast, during adolescence, the ligaments and other soft structures around the joint are two to five times stronger than the physis. Therefore, damage to the physis is more common than damage to ligaments in those with immature skeletons.

It is also important to note that adolescent bone is less dense, more porous, and more vascular than adult bone. Increased porosity contributes to prevent the spread of fractures. The pediatric skeleton has a number of other advantages including the capacity for rapid and predictable fracture healing, increased tolerance of long-term immobilization, and increased tendency to recover soft tissue mobility spontaneously following most injuries, and joint surfaces are generally more tolerant of irregularity than those of adults.

Not only is the skeleton growing during adolescence but there are profound changes in height, weight, muscle mass, motor skills, and coordination. The adolescent growth spurt is variable in its onset and duration. As a result, two individuals of the same size could have vastly different bone and muscle maturity leading to a size–size mismatch in sports. In collision sports such as football, size–size mismatch is magnified and leads to an increased risk and severity of injury for the less developed individual. Size–size mismatch is more pronounced in boys than girls because as girls experience only a slight increase in muscle strength after menarche boys continue to acquire muscle strength throughout adolescence. Similarly in girls, motor performance remains relatively constant throughout adolescence where as boys continue to see improved motor performance throughout adolescence. While there is no clear pattern of strength and motor skill development in girls, there appears to be a positive correlation between biological maturity and muscle strength and motor performance in boys. This positive correlation suggests that as an athlete matures, they acquire a greater skill level in their sport which can lead to a higher level of competition played at a higher intensity. Furthermore, as athletes mature, their maximal speed increases leading to more violent collisions with increased momentum. Both increased intensity and speed in collision sports add to the risk and severity of injury.

While the focus of this chapter has been the physical injuries adolescents’ experience, equally important are the psychological aspects of sports and injuries. Youth play sports for a variety of reasons including social acceptance, love of the sport, and hope of obtaining an athletic scholarship to college. With much pressure on athletes to perform at a high level whether it is from self, coach, friends, or family injuries can often be unexpected, difficult, and stressful. Most athletes have the proper motivation and desire to go through rehabilitation and get back to their sport as soon as possible. However, some athletes stagnate and may become depressed and require extra support to get through their injury. Athletes may go through a series of reactions after an injury similar to the context of death or other loss. The stages go in order from disbelief, denial, isolation, anger, bargaining, depression, to acceptance, and resignation with hope. During the recovery process, the physician must continue to motivate the athlete, help the athlete understand realistic outcomes, and listen to and manage the patient’s reactions.

It is estimated that 15–20  % of all injuries to long bone are acute injuries of the growth plate. A large number of these acute injuries happen during sports participation. Acute injuries of the growth plate in the upper extremity are twice as common compared to those of the lower extremity. Boys suffer more acute injuries, and the greatest number of injuries for boys occurs at the age of 12 and 13, whereas for girls, the greatest number of injuries occurs at the age of 11. A system called the Salter–Harris classification was developed to classify acute injuries to the growth plate in adolescents. The Salter–Harris scheme is the most widely used system and has practical use in treatment and prognosis.

There are five types of Salter–Harris fractures that increase in severity from 1 to 5. A Salter–Harris type 1 fracture is least severe and is a transverse fracture across the growth plate commonly through the hypertrophic zone. The metaphyseal and epiphyseal bones are spared from fracture. Since the normal osteogenesis in the reserve and proliferative zones remain undisturbed in a Salter–Harris type 1 fracture, the prognosis is good. Type 1 Salter–Harris fractures are known for their rapid healing time, and a gentle reduction followed by alignment to protect the bone and joint from displacement is usually satisfactory for treatment. With protection, only 4–6 weeks are needed for the fracture to heal.

A Salter–Harris type 2 fracture transverses the growth plate much like a type 1 fracture; however, the fracture also enters the metaphysis. As in type 1 fractures, the reserve zone and zone of proliferation are undamaged and therefore the treatment is the same as a type 1 fracture. Salter–Harris type 3 and 4 fractures occur from sheer forces and differ from less severe fractures in that the fracture crosses the epiphysis into the joint. The articular joint is disrupted as the proliferative zone is violated. Long-term problems associated with type 3 and 4 fractures are growth arrest and high risk of articular degeneration. Surgical intervention is often indicated for type 3 and 4 fractures. A Salter–Harris type 5 fracture results from a crush injury to the reserve or proliferative zones of the growth plate and can cause growth arrest.

Acute patellar dislocation is one of the most common causes of acute hemarthrosis in the young athlete. When comparing patellar dislocation in male and female patients, some studies have suggested similar rates (Hinton & Sharma, 2003), and others have demonstrated that females have higher dislocation rates in the under 18 age group (Fithian, Paxton, Stone, et al., 2004). Risk factors for patella dislocation include ­ligamentous laxity, increased genu valgum, patella alta, lower extremity version abnormalities such as femoral anteversion and external tibial torsion, trochlear dysplasia, increased quadriceps angle, foot pronation, and patellar tilt (Hinton & Sharma, 2003). Both the medial retinaculum and the medial patellofemoral ligament (MPFL) are primary restraints to patellar dislocation. The risk of recurrent patellar dislocations appears to be significantly higher in females. A prospective cohort study following 189 pts were followed for 2–5 years. The group with the highest risk of dislocation was females age 10–17 years; 61  % dislocations occurred during sports and 9  % during dancing (Fithian et al., 2004). Standard knee radiographs should be taken to evaluate for osteochondral injuries, avulsions of soft tissue fragments, patella height, and trochlear dysplasia. MRI is also useful to evaluate for significant soft tissue injuries. Initial treatment consists of a brief period of immobilization followed by early rehabilitation. A recent prospective study on surgical intervention for first-time dislocators in children/adolescents did not demonstrate better outcomes compared with nonsurgical management (Palmu, Kallio, Donell, Helenius, & Nietosvaara, 2008). For patients with recurrent symptomatic patellar instability, surgical intervention may be beneficial.

Traumatic shoulder dislocations occur primarily in collision and contact sports in young athletes. It has been estimated that around 40  % of shoulder dislocations occur in patients younger than 22 years of age. A significant challenge to treating physicians is the fact that athletes with a history of pediatric dislocation have a 90  % chance of recurrent dislocation (Bishop & Flatow, 2005; Deitch, Mehlman, Foad, Obbehat, & Mallory, 2003; Rowe, 1956). This is theorized to be due to the fact that pediatric dislocations are believed to stretch the capsule and diminishes its ability to provide support for the shoulder joint. Surgical treatment of shoulder instability has been shown to be generally successful in young patients (Chen, Diaz, Loebenberg, & Rosen, 2005). Physical examination in combination with diagnostic testing may demonstrate concurrent injuries of the anterior bony labrum or labral lesions (Bankart injury, superior labral anterior and posterior tear, Hill–Sachs lesions), rotator cuff tears, and subscapularis or lesser tuberosity avulsions. Three view radiographs of the shoulder including an anterior–posterior, Scapular-Y, and axillary lateral can help determine direction of dislocation and any other bony abnormalities. MRI arthrogram is useful for evaluating capsular and labral tissues. In the acute setting, immediate reduction of the dislocation shoulder be attempted. If successful, physical therapy protocol should be initiated for strengthening and range of motion. Treatment of first-time dislocation in high-risk athletes remains controversial, and there is some evidence that early surgery may play a role in reducing the risk of secondary dislocation (Bedi & Ryu, 2009). Families should be counseled about the high risk of recurrent instability episodes with possible surgical intervention if nonsurgical treatment fails.

The treatment of anterior cruciate ligament (ACL) injuries in skeletally immature patients remains controversial. Recent studies indicate that the incidence of this injury may be increasing, and young female athletes start sustaining these injuries in significant numbers around 12–13 years of age. Nonsurgical treatment has historically shown to have poor results due to inherent instability leading to meniscal (particularly medial) and chondral injuries (Graf, Lange, Fujisaki, Landry, & Saluja, 1992; McCarroll, Shelbourne, Porter, Rettig, & Murray, 1994). One of the most challenging aspects of surgical reconstruction involves prevention of physeal injury leading to growth disturbance (Kocher, Saxon, Hovis, & Hawkins, 2002). Several physeal sparing techniques have been described in patients with significant growth remaining. For older patients, different techniques using grafts crossing the physis have been described. A recent study of patients at Tanner stage 3 or 4 who underwent ACL reconstruction using transphyseal technique demonstrated no physeal complications with excellent clinical outcomes (Kocher, Smith, Zoric, Lee, & Micheli, 2007).

Tibial eminence fractures occur predominantly in the skeletally immature patient. The mechanism of injury is similar to that of the previously described ACL injury. They are classified into three types: type I, minimal displacement of tibial eminence; type II, displacement of anterior third to one half of the tibial eminence, producing a beak-like deformity on the lateral radiograph; and type III, the avulsed tibial eminence is completely lifted from the underlying bone (Meyers & McKeever, 1987). A rare fourth kind has been described with complete rotation of the fragment. Entrapment of the intermeniscal ligament or anterior meniscus is possible, which may be an impediment to reduction of these fractures (Kocher, Micheli, Gerbino, & Hresko, 2003). These fractures may be associated with other soft tissue injuries, including bone contusions, ligament injury, and meniscal tear (Monto, Cameron-Donaldson, Close, Ho, & Hawkins, 2006).

Fractures of the medial epicondyle of the elbow are more common than frank elbow dislocations and account for 10  % of elbow fractures in children. The ulnar collateral ligament may avulse the medial epicondyle during elbow trauma. Nearly 50  % of medial epicondyle fractures are associated with dislocation of the elbow; the displaced fragment can then become incarcerated in the joint, preventing a concentric reduction. Acute medial epicondyle fractures and dislocations of the elbow can occur in young gymnasts, and isolated medial epicondyle fractures are occasionally seen in adolescent pitchers (Caine & Nassar, 2005). Nondisplaced fractures are treated with casting. In athletes such as throwers, gymnasts, and wrestlers who place high physical demands on the elbow, anatomic reduction of medial epicondyle fractures may be important for future athletic performance.

Overuse injuries are common in adolescents who participate in sports. Repetitive activities can lead to tendinopathies, many of which have terms related to various sports such as golfer’s or tennis elbow (medial and lateral epicondylopathy, respectively). Tendinopathies can occur throughout the body. The histopathologic changes vary from the early stages of inflammation (tendinitis) to chronic noninflammatory, fatty degeneration (tendinosis). Treatment options start with conservative treatments such as rest, physical therapy, and anti-inflammatories. Individuals with symptoms refractory to more conservative treatment or those who need more aggressive therapy due to the need to perform at a high level such as professional or collegiate athletes can consider treatments such as ultrasound, steroid or platelet-rich plasma injections, or surgery.

Overuse can result in osteochondroses in adolescents due to their skeletal immaturity. These pathologic conditions involving the physis can occur in various area such as Osgood–Schlatter disease of the tibial tubercle apophysis, Sever’s disease of the calcaneus, osteochondritis dissecans of the capitellum of the elbow, and Little Leaguer’s elbow (medial epicondyle of the humerus). Treatment for these conditions primarily involves rest and anti-inflammatories/analgesics. If displaced or fragmented, surgery may be required.

Prevention has been more of a recent focus, especially in the case of Little League shoulder and elbow. In hopes of decreasing the incidence of these conditions, USA baseball released recommendations in the mid-1990s for youth pitchers limiting the number and types of pitches thrown depending on age (Benjamin & Briner, 2005). Pitchers 8–10 years old should be restricted to fastballs, 50 pitches per game, and 75 pitches per week (Benjamin & Briner, 2005). Pitchers 10–11 years old can start throwing changeups, 75 pitches per game, and 100 pitches per week. Pitchers 13–14 years old can start throwing curve balls and 125 pitches per week. They are still restricted to 75 pitches per game. Pitchers 15–16 years old can start throwing sliders, forkballs, splitters, and knuckleballs and 90 pitches per game. There are no restrictions for number of pitches per week starting at this age. Pitchers 17–18 years old can start throwing screwballs and 105 pitches per game.

Stress fractures are another type of injury that can result from overuse. Stress fractures are categorized into two groups depending on the etiology. Fatigue stress fractures are the result of abnormal stresses in normal bone (Dixon, Newton, & Teh, 2011). Insufficiency stress fractures occur due to normal stresses in abnormal bone such as those with anorexia or osteoporosis (Dixon et al., 2011). All young women who present with a stress fracture should be carefully screened for the female athlete triad which includes inadequate energy availability compared to energy used (formally defined as eating disorders such as anorexia), poor bone metabolism usually evidenced by the initial stress fracture (formally defined as osteoporosis), and hormonal imbalances leading to menstrual irregularities (formally defined as amenorrhea). The current thought is that the Triad is a continuum of these milder definitions up to and including the extreme definitions (see below).

Stress fractures can occur anywhere in the body but are most commonly in areas that provide support during weight-bearing activities such as the tibia, femoral neck, or pars interarticularis of the spine. This may also include the upper extremity in gymnasts. Runners are at increased risk of tibia and femoral neck stress fractures (Dixon et al., 2011; Harrast & Colonno, 2010). Spondylolysis, fracture of the pars interarticularis, is more common in wrestlers, gymnasts, and weightlifters (Dixon et al., 2011).

Images are needed to diagnose stress fractures. Radiographs often are nondiagnostic since the majority of stress fractures are nondisplaced and cannot be seen on normal X-ray films. Bone scans have been used historically to make the diagnosis; however, MRI is currently the gold standard since it may provide a better indication of the severity of injury and predict return to play.

Treatment of stress fractures depends on the nature and area of the injury. High-risk areas such as the femoral neck can have catastrophic consequences (i.e., displacement which may lead to necrosis of the femoral head) if not surgically stabilized. Stress fractures of the anterior tibia, proximal fifth metatarsal metadiaphyseal area, sesamoids, and navicular are at high risk of nonunion (Harrast & Colonno, 2010). Surgical stabilization should be considered. Otherwise, nonoperative treatment with rest or bracing can be implemented.

Child abuse is an area that treating physicians should remain vigilant for when evaluating musculoskeletal injuries. Abuse in adolescents may not be as difficult to assess as it is in children who have limited speaking ability. Child abuse as described in “The Child Abuse Prevention and Treatment Act” (CAPTA) amended by the “Keeping Children and Families Safe Act of 2003” is any recent act or failure to act, on the part of the parent or caretaker which results in death, serious physical or emotional harm, sexual abuse or exploitation, or an act or failure to act which presents an imminent risk of serious harm (Sink, Hyman, Matheny, Georgopoulos, & Kleinman, 2011). A child is a person under the age of 18 years, unless the child protection law of the state in which the child resides specifies a younger age for cases not involving sexual abuse.

Skin injuries are the most common manifestation of physical abuse. Burns are present in 10–25  % of cases, and bruising is found in 50–75  % of abuse victims (McMahon, Grossman, Gaffney, & Stanitski, 1995; Sink et al., 2011). Bruising in different stages should increase suspicion for abuse. In adolescents, there are no classic injuries that are specific of physical abuse like metaphyseal corner fractures in younger children or femur fractures in children less than one.

As briefly mentioned above, adolescent girls especially those in aesthetic sports (ballet, rhythmic gymnastics, synchronized swimming, and figure skating) or those sports who have weight categories or in which weight plays a role (crew, ski jumping, wrestling) are at increased risk for a condition termed the female athlete triad. The American College of Sports Medicine (ACSM) in 1992 first developed a special task force to look into the relationship among disordered eating, amenorrhea, and osteoporosis in female athletes, termed the female athlete triad (Beals & Meyer, 2007). They later developed a position paper on the female athlete triad, calling for more research (Beals & Meyer, 2007; Otis, Drinkwater, Johnson, et al., 1997). The new ACSM definition has now replaced disordered eating with low energy availability, amenorrhea with hormonal dysfunction and menstrual irregularities, and osteoporosis with poor bone metabolism and osteopenia which often presents as a stress fracture (Hoch et al., 2009; Otis et al., 1997). One study found that 78  % of high school female athletes had at least one component of the disorder. Only 1 of the 80 athletes had all three components (Hoch et al., 2009). Due to the relative high mortality that occurs in the most severe cases, the clinician should carry a high sense of suspicion when evaluating female athletes with any or all of the components.

Weight training in adolescents anecdotally is thought to be a concern due to the risk of growth disturbances and injuries. However, studies have shown little to no evidence that resistance training will negatively impact growth or maturation (Faigenbaum et al., 2009; Malina, 2006). Resistance training programs are safe overall with low incidence of injury. In one study of 354 middle school and high school football players, the injury rate was 0.082 injuries per person-year (Risser, Risser, & Preston, 1990). Lower back strain is the most prevalent injury in adolescents participating in weight training (Faigenbaum et al., 2009; Risser et al., 1990).

Supervision, good technique, and safe training equipment are important measures to prevent injuries in adolescents (Faigenbaum et al., 2009; Malina, 2006; Risser et al., 1990). Studies have shown that there is an increased risk of injury when home exercise equipment is used (Faigenbaum et al., 2009).

Motor vehicle accidents are the leading cause of death in adolescents in the United States, comprising 32  % of all deaths and 70  % of unintentional deaths (Sleet, Ballesteros, & Borse, 2010). Fatal injuries are more likely to occur when seat belts are not used, the driver has been drinking, or an inexperienced driver is driving other teenagers (Chen, Baker, Braver, & Li, 2000; Quinlan, Brewer, Sleet, & Dellinger, 2000; Sleet et al., 2010). Proper use of a seat belt could prevent around 40–60  % of motor vehicle deaths (Cummins, Koval, Cantu, & Spratt, 2008; Sleet et al., 2010). Unfortunately, adolescents are among the highest demographic of people who do not wear seat belts. In 2007, 11.1  % of high school students reported never wearing seat belts (Eaton et al., 2008; Jones & Shults, 2009; Sleet et al., 2010). Nonuse was more prevalent in males and African American students. The good news is that in addition to preventing mortality, seat belts prevent morbidity in motor vehicle accidents. Seat belt use results in a reduction in maxillofacial and lower extremity injuries (Cox et al., 2004). Restrained occupants had relative risks of 0.42, 0.28, 0.35, and 0.49 compared unrestrained occupants for maxillofacial, pelvis, femur, and tibia/fibula fractures, respectively (Cox et al., 2004; Estrada, Alonso, McGwin, Metzger, & Rue, 2004).