Swollen shoulder or swelling in or around the shoulder joint can be from a direct impact like a contusion. There may be specific local swelling on the top of the shoulder as in an acromioclavicular (AC) joint sprain, or general swelling in the shoulder joint which would accompany a dislocation or other acute shoulder injury. Swelling can also be through an arthritic joint or a muscle rupture, which can look swollen but can be hard to touch in some cases. Swelling can also occur with a rotator cuff or cartilage injury and can be associated with pain. Some medical conditions through infections or bites can also cause shoulder swelling and can also cause redness.