Shoulder pain is most often caused by an injury to the rotator cuff, a group of tendons and muscles that stabilize the joint. The rotator cuff develops wear and tear with age, and can be easily injured. When this happens, we compensate by using different muscles to pick things up or reach for them. “This may cause both shoulder and neck pain,” says Dr. Ricchetti. You may have a rotator cuff injury or other shoulder problem if pain: Develops in the shoulder itself or on the outside of your upper arm.