Causes / typical injury mechanism: Little League shoulder is an overuse injury involving stress at the proximal humeral physis (growth plate). It has also been called proximal humeral epiphysitis, proximal humeral epiphysiolysis, or proximal humeral epiphyseal plate rotational stress fracture (Salter-Harris type 1). The mechanism of injury involves torque and distraction forces stressing the hypertrophic zone of the physis, which is its weakest portion. These forces exacerbate the shoulder, especially during the late cocking phase of throwing, when the shoulder is in maximal external rotation.

Classic history and presentation: This condition presents as gradual pain at the proximal humerus as a result of overtraining / overuse for athletics. Pain is exacerbated by shoulder abduction and rotation (both external and internal).

Prevalence: Little League shoulder is a common condition seen in skeletally immature patients aged 11-16 years. It occurs more predominantly in boys than girls.

Risk factors: It is typically seen in young baseball pitchers (overhead athletes), but it is also seen in those who participate in tennis, volleyball, badminton, swimming, and gymnastics.

Pathophysiology: Repetitive rotational and distractive force at the physis causing a Salter-Harris type 1 injury. Sometimes the epiphysis can also be involved in extreme cases.

Recent studies have shown that repetitive throwing with this condition may eventually change the rotational axis of the humeral head with an increase in humeral retroversion (this can result in increased shoulder external rotation and decreased internal rotation, with total range of motion maintained).