An AC (acromioclavicular) joint sprain is an injury that damages the ligaments in the AC joint, which is where the shoulder blade meets the collarbone. The highest point of the shoulder blade is called the acromion, and strong tissues called ligaments connect the acromion to the collarbone, forming the AC joint. AC joint sprains can occur due to accidents or injuries that force the AC joint apart, such as falling onto the shoulder, falling onto an outstretched hand, or getting a direct blow to the shoulder. 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 depends on how serious the strain is and may include rest, wearing a sling, applying cold packs, taking prescription or over-the-counter medicines, and undergoing physical therapy.