If any other condition decreases the amount of space between the acromion and the rotator cuff tendons, the impingement process may get worse. Bone spurs can reduce the space available for the bursa and tendons to move under the acromion. The AC joint is directly above the bursa and rotator cuff tendons. In some people, the space is too small because the acromion is oddly sized . In these people, the acromion tilts too far down, reducing the space between it and the rotator cuff.
Impingement syndrome causes generalized shoulder aches in the condition's early stages.
It also causes pain when raising the arm out to the side or in front of the body. Most patients complain that the pain makes it difficult for them to sleep, especially when they roll onto the affected shoulder. A reliable sign of impingement syndrome is a sharp pain when you try to reach into your back pocket. As the condition worsens, the discomfort increases. The joint may become stiffer.