There can be a number of reasons contributing to the pain in your shoulder. There are three bones, four tendons, four muscles, and many other soft tissues that contribute to our shoulder joint.
When one or more of these structures are improperly aligned, they can press and injure other structures. Inflammatory conditions such as tendinitis, bursitis, or arthritis can be involved with shoulder impingement. Progression of the shoulder impingement can lead to further injury such as rotator cuff tears.
Oftentimes, the rotator cuff becomes inflamed from overuse or damage from a bone spur. The fluid-filled cushion called a bursa becomes inflamed. As the space narrows, the rotator cuff will be damaged causing irritation and pain when you raise your arm.
