An AC (acromioclavicular) joint sprain occurs when an injury damages the ligaments in the AC joint, which is where the shoulder blade meets the collarbone. This type of injury is common in athletes and can result from a direct hit to the shoulder or a fall. Symptoms of an AC joint sprain can vary depending on how serious the injury is and may include shoulder pain, soreness, swelling, bruising, change in the shoulders shape, bulge above the shoulder, shoulder that appears to droop, collarbone that moves upward, and limited movement in the shoulder. Treatment for an AC joint sprain will depend on how serious the strain is and may include rest, sling, cold packs, prescription or over-the-counter medicines, arm and shoulder exercises, and physical therapy.