Sports injuries would be the main cause of posterior instability/ tears. They are sometimes witnessed in younger Lively people. Sports for instance pounds-lifting, baseball, tennis or volleyball etcetera are popular causes of the injury. AC joint dislocations are labeled into unique grades. Grade I may involve rest and therapy, though https://www.theorthopaedicandpainpractice.com/is-my-shoulder-pain-caused-by-an-acromio-clavicular-dislocation/?_gl=1*xbbxlb*_up*MQ..&gclid=Cj0KCQjwkt6aBhDKARIsAAyeLJ2krYJSOuy5mZksrNqH-VDjQwW1ScD49yD8BUWysDG6u6bJPCSbXVUaAuCPEALw_wcB