Pediatric Annals

Special Issue Article 

Care of Shoulder Pain in the Overhead Athlete

Joseph Chorley, MD, FACSM, FAAP; Richard E. Eccles, MD; Armand Scurfield, MD

Abstract

Shoulder complaints are common in the overhead athlete. Understanding the biomechanics of throwing and swimming requires understanding the importance of maintaining the glenohumeral relationship of the shoulder. Capsular laxity, humeral retrotorsion, glenoid retroversion, glenohumeral internal rotation deficit, and scapular dyskinesis can all contribute to shoulder dysfunction and pain. Injuries are more likely during peak height velocity, especially when coupled with overuse, previous injuries not adequately treated, or change in the demands on the shoulder such as a new technique, bigger field, or longer race. Working with physical therapists, athletic trainers, and coaches to identify and treat the etiology of the shoulder dysfunction will help pediatricians return the athlete to activity and prevent future injury. [Pediatr Ann. 2017;46(3):e112–e119.]

Abstract

Shoulder complaints are common in the overhead athlete. Understanding the biomechanics of throwing and swimming requires understanding the importance of maintaining the glenohumeral relationship of the shoulder. Capsular laxity, humeral retrotorsion, glenoid retroversion, glenohumeral internal rotation deficit, and scapular dyskinesis can all contribute to shoulder dysfunction and pain. Injuries are more likely during peak height velocity, especially when coupled with overuse, previous injuries not adequately treated, or change in the demands on the shoulder such as a new technique, bigger field, or longer race. Working with physical therapists, athletic trainers, and coaches to identify and treat the etiology of the shoulder dysfunction will help pediatricians return the athlete to activity and prevent future injury. [Pediatr Ann. 2017;46(3):e112–e119.]

According to one study, when third-year pediatric residents were surveyed about teaching of the musculoskeletal examination, the shoulder was ranked lowest.1 Shoulder complaints and their examination in pediatric athletes can be challenging. In the high school athlete, shoulder injuries account for 7% of all sports injuries and 13% of baseball injuries.2 Overhead athletes (throwers, swimmers, volleyball players, and tennis athletes) have shoulder complaints related to the “thrower's paradox,” which is the delicate balance between the need for upper extremity mobility to perform, and sufficient stability to prevent injury.3 Anatomy and biomechanics of the shoulder are complicated, but by understanding injury patterns and performing an appropriate history and physical examination, clinicians can identify the etiology of the problem. By working with physical therapists, athletic trainers, and coaches to address the causes of the injury, pediatricians can optimize treatment and prevent further injury.

Anatomy

The glenohumeral (GH) joint is the location of most overhead athletes' shoulder problems. The muscles, bones, and capsular structures of the shoulder work together to maintain mobility and stability of the GH joint. The anatomy of the shoulder is analogous to a golf ball (humeral head) on a tee (glenoid). Only one-third of the humeral head contacts the glenoid fossa. Contact surface area and stability are increased by the labrum, a cartilaginous bumper around the circumference of the glenoid. The joint capsule is thin but it has thickened areas that form the small GH ligaments. The anterior and posterior inferior GH ligaments serve as static stabilizers. The four rotator cuff (RC) muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) are the most important dynamic stabilizers and envelop the humeral head, making micro-adjustments to maintain proper glenohumeral alignment. The supraspinatus muscle is the primary humeral head depressor that prevents the humeral head from impinging the structures of the RC interval (supraspinatus, tendon of the long head of biceps, coraco-acromial ligament, subacromial bursa) on the acromion. The teres minor and infraspinatus are external rotators that work to balance the larger, stronger internal rotators (latissimus dorsi, pectoralis major, subscapularis). The glenoid is attached to the scapula; therefore, scapular motion and periscapular muscle strength are important for placing the glenoid in proper position so other structures are not injured or overworked (trying to keep the ball on the tee). Muscles contributing to scapular motion include the levator scapulae, serratus anterior, trapezius, rhomboid, and pectoralis minor. Because the scapula articulates with the thoracic rib cage, poor forward flexed posture will result in the scapula tipping forward, causing the acromion to collapse on the structures of the RC interval.

Repetitive stress from overhead sports can gradually lead to anatomic changes in the shoulder, such as stretching of the capsule and humeral retrotorsion. A stretched capsule causes excessive motion of the humeral head with relationship to the glenoid4 (increased laxity), which can lead to instability (shifting out of place) or impingement (pinching of soft tissue structures). Repetitive rotational stress will result in the humerus twisting into extra external rotation (humeral retrotorsion) and hitting the posterior glenoid rim, resulting in posterior tipping (glenoid retroversion). A thrower's dominant shoulder will usually develop at least 5° of extra external rotation compared to the nondominant shoulder. This extra external rotation (ER) is a physiologic adaptation that allows for additional ER without the humerus having to rotate further. Extra ER range allows more time for the shoulder to get to peak velocity during the acceleration phase (less strain on the shoulder).5,6 However, the same repetitive stress will result in injury and scarring to the posterior inferior GH ligament, restricting internal rotation (IR). Glenohumeral internal rotation deficit (GIRD) has been defined as a loss of IR of 20° or more, and has been associated with increased risk for shoulder and elbow pain.5

Scapular dyskinesis (deviation of the normal scapular position with shoulder movement) is an important and often missed etiology of shoulder impingement. The most common type is inferior medial scapula dysfunction, which results in the acromion collapsing into the rotator cuff interval. Weak inferior trapezius, tight pectoralis minor, and forward flexed posture contribute to scapular dyskinesis.7

Patient History

A thorough patient history is helpful in discerning the etiology and diagnosis of an overhead athlete's problem. Duration, location, severity, and distribution of pain help to discern contributing factors. Neck pathology must always be considered. Mechanical sensations (eg, popping and clicking) that are nonpainful are common in normal shoulders. Painful mechanical sensations, however, are usually significant. Joint instability (shifting sensations between the shoulder bones) can indicate that the GH stabilizers are not strong enough to meet the demands of the activity. Other factors that must be considered include the following:

  1. Age: Peak height velocity (boys age 12–16 years, girls age 9–13 years) results in rapid changes in body geometry. Proprioception and flexibility deficits that commonly occur during rapid growth can contribute to their inability to perform their sport correctly.

  2. Volume: Overtraining is common in young athletes, especially those who participate on multiple teams. Each team may not account for training volume of the others. Early in the season, the amount of training is significantly higher in volume and intensity than in the off-season. “Moving up” to the next level comes with larger field size, swimming longer races, and higher expectations about training ability.

  3. New technique: New techniques take time to perfect and require diligent work and guidance. Transitioning to a jump serve in volleyball, throwing a slider in baseball, or learning new strokes in swimming can be challenges that contribute to injury.

  4. Previous injury: Previous injury predisposes to reinjury. Compensation can cause stress at a different point in the kinetic chain (eg, hip pain can lead to shoulder injury).

Diagnoses

Anterior Impingement, Rotator Cuff Tendonitis, Subacromial Bursitis, and Biceps Tendonitis

Anterior shoulder impingement is caused by the pinching of the structures of the rotator cuff interval between the humeral head and the acromion.8 Impingement will result in rotator cuff/biceps tendonitis and/or subacromial bursitis.9 Maximal shoulder impingement occurs when the humerus is internally rotated in the forward flexed overhead position (streamline swimming position). The humeral head can migrate superiorly with supraspinatus dysfunction or the acromion can tip inferiorly with periscapular muscle weakness. Patients complain of anterior shoulder pain with overhead activities that may localize to the anterior or lateral deltoid. Treatment includes rest from painful activities and correcting the muscle strength imbalances, followed by gradual transition back to activity once pain resolves. This may take a few weeks to a few months, depending on the number of etiologies contributing to the dysfunction.

Labral Tears

Labral injury may present with deep, poorly localized pain with activity. Labral shoulder pain is similar to anterior impingement but does not respond to typical treatment for impingement. Painful catching, locking, or “popping” with overhead sports activities are classic complaints in patients with labral tears.10 The superior labrum anterior to posterior (SLAP) tear is more common in throwers because of the result of repetitive compressive and shear forces on the superior labrum from the throwing motion.11 A magnetic resonance imaging scan with intra-articular contrast can confirm a labral tear,12 which will typically require surgical treatment.

Posterior Impingement

Posterior impingement presents with posterior/lateral shoulder pain, primarily in throwing athletes when the shoulder is abducted and maximally externally rotated (late cocking throwing position). This position compresses the supraspinatus, infraspinatus, and the glenoid rim. These athletes may have GIRD, and specifically insufficient ER.5 Treatment includes rest from painful activities, capsular stretching, and correcting any muscle strength imbalances, followed by gradual transition back to activity once pain resolves. Symptomatic improvement with proper treatment should be seen in 2 to 4 weeks.

Little League Shoulder

Little League shoulder is an osteochondrosis or stress injury of the proximal humeral epiphysis that is being diagnosed with increasing frequency.13 Athletes will complain of pain at the top of the arm with throwing and have decreased throwing velocity. On physical examination, there is tenderness when the examiner squeezes the humeral head. Radiographs are not required for the diagnosis, but if performed may demonstrate widening and sclerosis at the growth plate. Treatment is rest from throwing until no longer painful with activity or tender to palpation (usually takes at least 4–6 weeks), followed by gradual return to throwing. Rehabilitation exercises to correct any strength imbalances (eg, scapular winging) and correction of any technique errors (Table 1) can help prevent recurrence, along with following appropriate pitch count guidelines.14


            Common Throwing Errors and the Resulting Symptoms

Table 1.

Common Throwing Errors and the Resulting Symptoms

Biomechanics

The biomechanics of overhead motion in throwing a baseball, serving a volleyball, hitting a tennis ball, or generating a swim stroke involve more than the upper extremity. The lower extremities and trunk generate and transfer energy to the upper extremities for optimal sports performance.15 For example, linear and rotational force of the lower extremities and trunk account for 50% to 60% of the total force generation required for throwing.16

Throwing

Throwing has six distinctive phases: (1) windup, (2) early cocking/stride, (3) late cocking, (4) acceleration, (5) deceleration and (6) follow through17,18 (Table 1). Each phase subjects the upper extremity to varying forces and loads.

In the windup, potential energy is stored in the rotated torso when bringing the lead leg to maximum hip flexion and adduction while balancing on the back leg. Injury risk in this phase is minimal, but lack of balance and proprioception can lead to increased shoulder torque and possible injury during later phases.19

With a baseball pitcher, the stride/early cocking phase initiates the forward momentum. The shoulder is abducted, extended, and begins to externally rotate while the elbow extends, usually showing the ball to the shortstop (if the pitcher is right handed). The lead hip is abducted and ER occurs to position the foot pointing toward home plate. Injury can occur when striding incorrectly. Overstriding (further than pitcher's height) results in the inability to the rotate hips, which causes excessive force to the shoulder. Striding away from the pitching arm (“opening up”) causes the trunk to get ahead of the shoulder, overstretching the anterior shoulder capsule. Striding toward the throwing side subjects the labrum to excessive force.

Athletes will often complain of pain in the late cocking position. This phase of throwing is when the shoulder achieves maximal ER and has its maximum potential energy, but this is also the position of posterior impingement. The arm is externally rotated almost 160° to 170°, the lead leg acts to stabilize a fulcrum point, and the pelvis rotates to face the target. The throwing arm is maintained at 90° of abduction, and elbow at 90° to 100° of flexion.

The acceleration phase is when the stored potential energy is used to throw the ball toward the target. This phase starts with rapid IR of the shoulder and is terminated with ball release. The desired force from this violent motion stresses the IRs of the shoulder through strong concentric activation as the shoulder ERs contract eccentrically to maintain proper GH alignment.

The deceleration phase begins with ball release, dissipating the energy of the violent acceleration phase. This phase lasts until maximal internal rotation and terminal elbow extension is achieved. The forces on the superior labrum at the insertion of the long head of the biceps tendon during this phase can result in SLAP lesions. The large eccentric contraction needed to slow acceleration during this phase can strain the rotator cuff and posterior deltoid.

Follow through is the final phase that terminates throwing and positions the pitcher to be ready to field the ball.

Other Overhead Sports: Football, Water Polo, Volleyball

The throwing motion of an American football quarterback has a cocking phase that starts earlier and with less abduction than that of baseball pitchers. Football throwing injuries are less commonly due to overuse and typically result when the throwing motion is disrupted by an opponent. Volleyball athletes have similar stress but must also coordinate a running approach, jumping, and hitting the ball with feet off the ground. Water polo players have shoulder pain related to swimming mechanics as well as difficult throwing mechanics because their feet cannot touch the bottom of the pool.10

Swimming

Because competitive swimmers average around 30,000 strokes per shoulder per week, shoulder pain is common.20,21 With 90% of propulsive power coming from their upper extremities,21 swimmers will develop strong serratus anterior, latissimus dorsi, pectoralis major, and pectoralis minor muscles, resulting in the classic swimmer's posture (Figure 1). There are four strokes in competitive swimming: crawl (or “freestyle”), backstroke, butterfly, and breaststroke. Each stroke involves circumduction of the GH joint with varying degrees of IR and ER, and scapular protraction/retraction. Each stroke is divided into two main phases: pull-through and recovery. Pull-through, where most problems occur, is further split into four components: hand entry, catch, mid-pull, and finish. The recovery phase occurs above the water, starting when the hand exits and ending when the hand re-enters the water. Pain does not usually occur during recovery but errors can lead to problems during pull-through (Table 2).


            Typical swimmer's posture and associated muscle imbalances. Reprinted with permission from www.SwimmingScience.net.26

Figure 1.

Typical swimmer's posture and associated muscle imbalances. Reprinted with permission from www.SwimmingScience.net.26


            Technique Errors that Increase Risk for Shoulder Pain and Injury in Swimmers

Table 2.

Technique Errors that Increase Risk for Shoulder Pain and Injury in Swimmers

Regardless of their stroke specialty in competition, swimmers spend most of their practice time performing freestyle and backstroke, which are long axis strokes in which the trunk and hips rotate around the body's center axis (axial plane rotation). Adequate rotation and timing of reciprocating arm motion (one arm is pulling while the other is recovering) are extremely important to stroke mechanics and shoulder injury. Butterfly and breaststroke require both arms to recover at the same time. Trunk and hips will not rotate axially but will undulate in the sagittal plane. Because the trunk cannot rotate away from the arms during pull-through, the shoulder begins every pull-through phase in the anterior impingement position.

In freestyle, recovery phase requires scapular retraction/elevation and humeral abduction and ER while keeping the elbow high in the vertical plane. The pull-through phase starts at hand entry with scapular protraction, humeral adduction, and internal rotation (like raising your hand in class to answer a question). This is the anterior impingement position. If the scapula is not protracted, the acromion will collapse into the rotator cuff interval. With proper trunk rotation, the humerus is less adducted (raised arm now points to 1 o'clock instead of noon) and avoids impingement.

The backstroke has similar demands on the shoulder as freestyle, but the actions are reversed because the swimmers are on their backs. The pull-through phase begins with scapular retraction and humeral horizontal abduction and ER. This stroke places increased stress on the anterior capsule of the GH joint.20 The swimmer's trunk also rolls toward the side of the pull-through shoulder, and the elbow is now flexed during pull-through and extended during recovery.

The butterfly has similar shoulder activity to freestyle, but the arms are not alternating. This places a greater demand on the medial scapular stabilizers/retractors20 (rhomboids and trapezius muscles). The breaststroke also involves simultaneous movement at both shoulders. The pull-through phase begins with the shoulders in the impingement position. Catch begins with keeping the elbows high. The swimmer then supinates the hands and internally rotates the shoulders.21 With elbows flexed to 90°, the swimmer moves forward with their upper body out of the water while abducting and extending the shoulder. The swimmer then lunges forward, back under the surface of the water, just prior to a powerful forward propulsive kick.21 The swimmer's hands never move below the hips, resulting in the lowest lever-arm length and tensile force on the shoulder.20

Physical Examination

Related Structures

Assessment of the neck and cervical spine evaluates for possible referral source of shoulder pain. This begins with active range of motion through flexion, extension, rotation, and lateral flexion while assessing for pain. This is followed by palpation of the paraspinal muscles and spinous processes, evaluation of strength, neurovascular integrity, and presence or absence of pain with axial loading (Spurling's maneuver).

Inspection

Inspection of the shoulder requires that patients wear appropriate clothing so that landmarks can be identified (male patients can be shirtless, and female patients in tank top that adequately exposes the shoulder). The clinician should evaluate for muscular development, deformities or asymmetries, swelling, shoulder height, and scapular positioning (Table 3). Asymmetric development can be a clue to pathology. For example, the classic swimmer posture (Figure 1) with overdevelopment of the pectorals and latissimus at the expense of the lower trapezius and rhomboids, increases risk for anterior impingement. A patient sitting on the examination table, leaning back with their hands behind them for support usually indicates a weak and disengaged core. When standing behind the patient, a prominent inferior tip of the scapula can indicate poor scapular stability that can lead to GH pathology.


            Risk Factors for Shoulder Pain or Injury that Can Be Identified on Physical Examination

Table 3.

Risk Factors for Shoulder Pain or Injury that Can Be Identified on Physical Examination

Palpation

Tenderness over the proximal humeral physis indicates Little League Shoulder. Tenderness over the anterior joint line commonly occurs with anterior impingement, but also could indicate labral pathology. Posterior joint line tenderness is frequently related to posterior impingement, but could also indicate less common pathology such as anterior or posterior GH subluxation. When the humeral head subluxates, it is stretching the capsule and RC muscles, which can be tender on examination. Tenderness in the subacromial space is common with subacromial bursitis, anterior impingement, and RC tendonitis. Bicipital groove tenderness suggests biceps tendonitis.

Range of Motion and Strength Testing

Range of motion (ROM) and strength testing assess active and passive ROM, noting any asymmetry or restrictions. To assess per-scapular strength, have the patient abduct both shoulders to 180° and back several times, which can reveal scapular dyskinesis when viewed from behind. Resisted forward flexion in standing will produce pain in most shoulder injuries. However, if the pain resolves with repeat examination while supine, when the scapula is supported by the examination table, then peri-scapular muscle weakness is the likely etiology. Supraspinatus integrity and strength is evaluated with the “Empty Can” test. This test begins with the humerus at 90° abduction, maximally internally rotated (ie, thumb down), and 45° of horizontal flexion. The patient resists while the examiner applies downward pressure, noting any pain or weakness.

Passive ROM is optimally measured with the athlete supine, shoulder abducted to 90°, humerus on table, and elbow off table. Passive IR and ER on dominant and nondominant shoulders are measured (0° being perpendicular to the table). Ideally, the thrower's shoulder should have at least 5° more ER than the opposite shoulder and less than 20° loss of IR compared to the nonthrowing shoulder.5

Provocative and Stability Tests

Provocative and stability tests assist in diagnosing the potential shoulder etiology and help determine the need for advanced imaging (Table 4). Sensitivity and specificity vary with each test, with no test being ideal or the gold standard, so they should be used as a compliment to the elicited history and general examination already obtained.


            Provocative and Stability Tests for the Shoulder

Table 4.

Provocative and Stability Tests for the Shoulder

Treatment and Prevention

Treatment is based on the diagnosis, but generally requires rest from the irritating activity, while any muscle imbalances or biomechanical deficits are addressed (Table 4). A physical therapist experienced with treating upper extremity injuries in overhead athletes can be helpful. The thrower's 10 program22 is part of the rehabilitation program but also can be used by all overhead athletes to address some of the common biomechanical issues before they are injured. Once muscle imbalances are corrected and pain is resolved, an experienced coach can analyze the athlete's technique. Dedicated video analysis and biomechanical computer modeling can aid in identifying subtle technique errors. Return to sport can be considered when the patient has full range of motion and no pain with activities of daily living, no tenderness on physical examination, and has completed a progressive return to a throwing23,24 or swimming25 program.

Summary

Treating the overhead athlete requires understanding the biomechanics of the shoulder and correcting the underlying etiology of the shoulder dysfunction. Knowing the demands placed on the shoulder in overhead sports highlights how even small errors can result in injury. A team approach with physical therapists, athletic trainers, and coaches will optimize treatment and facilitate return to sport.

References

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Common Throwing Errors and the Resulting Symptoms

Phase of Throwing Common Errors Symptoms/Diagnoses Intervention/Treatment
Windup (starts with standing on the pitching rubber) Lack of stability in dominant leg Back/hip pain Shoulder pain later in throwing motion Single leg proprioception training Iliopsoas and hamstring stretching
Early cocking/stride Overstriding, stepping away or toward dominant arm (opening up) Early internal rotation of the forearm (“pie throwing”) Back/hip pain Shoulder pain later in throwing motion Loss of power Shorten stride Step toward home
Late cocking Lack of full external rotation Fatigue Posterior impingement Anterior glenohumeral instability Conditioning Fewer innings Core strengthening
Acceleration Dropping the elbow Arm behind hips Back pain from hyperlordosis Medial elbow pain Shoulder pain Keep shoulder abducted >100° (elbow high) Core strengthening
Deceleration and follow through Lack of flexion at the waist Biceps tendonitis Finish throwing motion by getting trunk over lead leg in a balanced position

Technique Errors that Increase Risk for Shoulder Pain and Injury in Swimmers

Technique Error Intervention
Stroke inefficiency (leading to early fatigue) Looking forward (causes hips to drop) Drop chin slightly to look at bottom of the pool
Shortened stroke Finish with hands below waist
Dropping elbows in pull through (“slipping water”) Keep elbows high to grab more water
Using excessive force Deep pull technique Elbows high but bent in mid-pull
“Windmill recovery” Use high elbows in recovery
Increased primary anterior impingement Flat shoulders Rotate hips and trunk around axis of the spine
Late breathing Breathe at hand exit
Hands crossing midline at hand entry Rotate hips/trunk Avoid swinging hands in recovery (keep elbows high in vertical plane next to the body)
Overreaching at hand entry to lengthen stroke Stretch from scapula and shoulder elevation not horizontal adduction

Risk Factors for Shoulder Pain or Injury that Can Be Identified on Physical Examination

Risk Factor Intervention
Poor posture Core strengthening of multifidus and transverse abdominus Stretch iliopsoas Improve thoracic mobility
Asymmetric muscular development Stretch pectorals and latissimus dorsi Strengthen lower trapezius and rhomboids
Posterior impingement Stretch posterior capsule Peri-scapular strengthening
Scapular dyskinesis Strengthen serratus, lower trapezius, rhomboids Stretch levator scapulae, pectoralis minor Improve thoracic mobility Address poor posture
Poor balance on single leg Strengthen core (gluteal and abdominal oblique muscles) Dynamic proprioceptive exercises
Decreased shoulder external rotation at 90° abduction Eccentric peri-scapular strengthening Progress to “Thrower's 10” program22
Supraspinatus weakness Strengthen but also look for other etiologies

Provocative and Stability Tests for the Shoulder

Test Action Results
Impingement
  Anterior impingement (Hawkin's test) Passively forward flex shoulder to 90° with elbow flexed to 90°, then passively internally rotate (this narrows the rotator cuff interval) Provoked pain over deltoid tubercle or anterior shoulder can indicate anterior impingement
  Posterior impingement Patient supine, arm abducted to 90° with maximal ER Provoked pain over posterior shoulder can indicate posterior impingement
Biceps testing
  Speed's test Patient attempts to forward flex shoulder against resistance while keeping their elbow extended and forearm supinated Pain at bicepital groove can indicate biceps tendonitis or GH instability
Labral tests
  O'Brien's test Patient's elbow extended and shoulder in 90° forward flexion, 40° horizontal adduction, and maximal internal rotation (thumb down). The patient resists the clinician's downward force. Examination is repeated with the thumb up (neutral position) Pain in IR position that goes away in ER position suggests labral pathology
  Crank test Apply axial load to the patient's 90° abducted shoulder while passively internally and externally rotating Pain, catching, or painful clicking is a positive test for labral injury
  Biceps load Patient starts with shoulder abducted and flexed elbow to 90°. The examiner maximally externally rotates the shoulder and then provides resistance against elbow flexion Worsening of pain or apprehension suggests labral pathology
Stability tests
  Sulcus sign Relaxed patient with arms at sides allows the examiner to pull arms while observing the shoulder Increased space between the acromion and humeral head indicates inferior GH instability
  Anterior/posterior drawer While grasping the humeral head with one hand and stabilizing the glenoid with the other, examiner translates the humeral head anteriorly and posteriorly with comparison to the opposite side Sagittal GH instability
  Apprehension (anterior) Supine patient's arm is passively abducted 90° and maximal ER applied Positive if patient experiences sense of instability
  Fowler's relocation After the apprehension test, examiner applies posterior force on the humerus If apprehension sensation is relieved, this further supports diagnosis of anterior GH instability
Authors

Joseph Chorley, MD, FACSM, FAAP, is an Associate Professor of Pediatrics, Baylor College of Medicine. Richard E. Eccles, MD, is a Fellow, Primary Care Sports Medicine, Baylor College of Medicine. Armand Scurfield, MD, is a Fellow, Primary Care Sports Medicine, Baylor College of Medicine.

Address correspondence to Joseph Chorley, MD, FACSM, FAAP, Associate Professor of Pediatrics, Baylor College of Medicine, 6621 Fannin Street, CCC 1710.00, Houston, TX 77030; email: jchorley@bcm.edu.

Disclosure: Joseph Chorley is a section editor and a contributing author for sports medicine for the UpToDate journal. The remaining authors have no relevant financial relationships to disclose.

10.3928/19382359-20170216-01

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