d5aa8617_University_of_Chicago_Medicine__Possible_cause
[Type of overuse injury] Little Leaguers' elbow or shoulder [Symptoms] Pain in the elbow or shoulder area, especially after activity [Possible cause] 
Repetitive overhead throwing maneuvers that cause damage and inflammation to the growth plates of the bones in the arm (or as a result of a fracture).
Overuse Injuries - The University of Chicago Medicine
Possible cause