Your rotator cuff is a group of tendons and muscles that connects the upper arm bone to the shoulder blade. The tendons attach the muscles to the bones and help provide stability. Rotator cuff tendonitis and bursitis occur when the tendons in your shoulder become inflamed or irritated. Rotator cuff irritation is often caused by repetitive reaching movements of the arms such as with gardening, raking, cleaning, shoveling and carpentry. Sports such as tennis, golf, baseball, softball and lacrosse can also have a cumulative effect on this area. Though often overlooked, poor posture over time can also predispose this area to injury because the shoulder is in a position that results in extra friction on the rotator cuff.