Children participate in sports on a regular basis as a means of activity, whether it be for fun or competition. The more children play any sport, the more likely they are to get injured. There are many factors that lead to injury, beginning with differences in anatomy & physiology compared to adults. Youth pitchers are throwing at a time when the epiphyseal plates are not close in the humerus and clavicle. Additionally, it has been shown that the tendons and ligaments in a child have a significantly greater amount of collagen type III compared to adults, contributing to capsular and ligamentous laxity. The combination of shoulder laxity and non-closed epiphyseal plates predisposes youth pitchers to shoulder injury.
    There are many contributing factors that can lead to shoulder injury in youth pitchers. The pitching mechanics have been studied extensively and are broken down into 6 phases. The extreme ranges and torques placed on the shoulder joint during the pitching motion excessively stress the tissues of the shoulder. It is debatable whether alterations in the mechanics of the lower body during a pitch can affect the shoulder joint. For a more in depth look at pitching mechanics, the reader is referred to The Athlete's Shoulder. Injury has been shown to be linked to altered throwing mechanics, fatigue, number of pitches (>75), and number of innings pitched. It is interesting to note that pitch type does not have an effect on injury.

    Some early signs of a shoulder injury to a pitcher involve pain with throwing, decreased pitch velocity, and decreased ability to locate pitches. When examining a pitches for injury, there are many items to take into consideration: shoulder motion, flexibility, strength, shoulder laxity, and additional parts of the kinetic chain.
    Proximal humeral epiphysiolysis has a common point of maximal tenderness over the lateral aspect of the proximal humerus. Radiographic findings consist of a widening of the proximal epiphysis of the humerus. Patients are advised to rest (one study recommended 6 weeks of no throwing with complete rests, followed by 6 weeks of no throwing during strengthening rehabilitation - totalling 3 months without throwing), be educated on proper pitching mechanics, and a strengthening program focused on the rotator cuff, periscapular muscles, and core musculature. A normal capsular pattern is also addressed during rehab.
    Due to the excessive mobility of the throwing shoulder, pitchers are predisposed to rotator cuff injuries, secondary shoulder impingement syndrome, and SLAP lesions. Rotator cuff injuries display pain during the release, deceleration, and follow-through phases of throwing. Patients typically report pain and weakness, especially decreased ROM during abduction with ER or IR. Pitchers may also display decreased velocity and precision. Additionally, these pitchers often show poor scapulohumeral control during pitching motions. When the patient is identified as having a rotator cuff injury, cessation of throwing activities is advised until symptoms disappear. As expected, rehabilitation includes strengthening of the rotator cuff and scapular stabilizer muscles, while addressing scapulohumeral control and ROM. Once the patient's strength and ROM are normal and pain-free, the patient can then commence a throwing program with reeducation of proper pitching mechanics.
    Secondary impingement shoulder, caused by weakness in the rotator cuff muscles and ligamentous laxity, displays pain in the anterior or anterolateral aspect of the shoulder, especially during overhead activities. Pain is especially profound during arm cocking and acceleration phases of pitching. These individuals are treated conservatively normally with strengthening the rotator cuff and scapular stabilizers.
    Symptoms associated with SLAP lesions include a dull aching sensation within the joint, pain and a catching feeling when throwing, trouble sleeping due to shoulder discomfort, and decreased pitch velocity. The pitcher will usually complain of pain during the cocking phase of the throw. (Remember with labral pathology to utilize the Active Compression test (O'Brien), Biceps Load II test,  and the Anterior Slide test). While these tests are useful, imaging can raise positivity in correct identification. However, MRIs should only be used once conservative treatment has failed. In adolescents, conservative treatment and rest is attempted before surgery and includes rest and physical therapy. Patients are limited from return to play until full ROM and strength are achieved without pain.

    Some general limitations recommended for injury prevention in adolescent pitchers include: avoiding pitching when arm fatigue or pain is present, refraining from throwing activities at least 3 months a year, not playing catcher and pitcher in the same game, not pitching 3 days in a row, and pitching for >1 team. For specific limits on the number of pitches thrown per game, mandated days of rest based on # of pitches thrown, and pitch limits, check out table 1 in the article.

    Pitchers are continuously doing something to prepare for their next game, even during the off season. During the off season, it is essential that the pitcher includes stretching, cryotherapy, and a global kinetic conditioning program in their training. Strength training is obviously included as well, especially due to the findings of weak ER and supraspinatus strength found in many pitchers. Rehab of the pitchers shoulder includes activities in 4 phases:Acute: cryotherapy, iontophoresis, ultrasound, e-stim, flexibility and stretching the posterior shoulder muscles, rotator cuff and scapular stabilization stretngthening, and dynamic stabilization exercises. No throwing.

Intermediate: stretching (especially IR and horizontal adduction of the shoulder), progressive isotonic strengthening and initiation of core lumbopelvic region and lower extremity strengthening.

Advanced Strengthening: previous components are continued, plyometric program, endurance drills, short distance throwing.

Return to Activity: exercises and modalities from prior stages, progressive interval throwing program to transition back to competitive throwing. During this phase a data-interval throwing program is utilized for the transition back to competitive throwing. Check out Table 2 in the article for the detailed steps. An alternate throwing program frequently used is a long-toss program. This is adequate as well, so long as maximal distance is not used due to the strain is places on the throwing mechanics.

Reference:
Zaremski, J., & Krabak, B. (2012). "Shoulder injuries in the skeletally immature baseball pitcher and recommendations for the prevention of injury." PM&R: The Journal of Injury, Function, and Rehabilitation, 4(7), 509-515.

The article actually found that in the asymptomatic right-handed pitchers, there was a significant difference in the thickness of the supraspinatus tendon, the dominant arm tendon being thicker. No such difference was found in left-handed pitchers. This could be a significant finding in realizing the misdiagnosis that could occur by simply using tendon thickness as the basis for identifying a pathology. One of the limiting factors of the study was the fact that it was simply a cross-sectional observational study of 12 pitchers. With the low participant rate, it is unknown how much the results of this study can be applied to a larger population, but it will hopefully lead to further investigation into the area. While the study does not establish any significant tendon thickness norms (due to the small sample size and study design), it brought the potential of misdiagnosis into the focus for further consideration.