The looseness is generally a result of repetitive overhead motion when swimming and playing tennis, for example.  A shoulder dislocation occurs when the head in the humerus (higher arm bone) is forced out with the socket of the shoulder blade. This can transpire from a direct blow towards the shoulder, https://www.theorthopaedicandpainpractice.com/what-are-shoulder-joint-dislocations/?_gl=1*164kc8h*_up*MQ..&gclid=Cj0KCQjwkt6aBhDKARIsAAyeLJ2krYJSOuy5mZksrNqH-VDjQwW1ScD49yD8BUWysDG6u6bJPCSbXVUaAuCPEALw_wcB