The shoulder has a greater range of motion than any other joint in the body. prone to injury The large deltoid muscle moves the shoulder most of the power. (subscapularis, supraspinatus, infraspinatus and teres minor. They are attached to the bone by tendons. The joint is made up of muscles and tendons that attach the arm to the shoulder joint and allow the arm to move. Rotator tendonitis is an inflammation of the tendons of the shoulder. Prolonged inflammation or injury can cause a tendon tear. Common names for shoulder tendonitis include shoulder impingement syndrome, tennis shoulder, pitcher's shoulder, and swimmer's shoulder.