Degree of shoulder separation
Shoulder separation is classified by the degree of torn ligaments involved: Grade I: Minor displacement of the joint in which the AC ligament is stretched or partially torn, but the CC ligament is not injured. This is the most common type of AC joint injury. Grade II: Partial dislocation of the joint in which the AC ligament is completely torn, while the CC ligament is uninjured or only partially torn. Grade III: Complete separation of the joint in which the AC and CC ligaments are completely torn, and the clavicle and the acromion are completely separated. A bump is often visible on the shoulder where the clavicle is pushed up. Grades IV –VI are uncommon and usually involve tears in the deltoid and trapezius muscles requiring surgery. Shoulder dislocations can be a recurring problem after tendons, ligaments, or muscles become loose or torn.