Final answer:
Tendinitis is the inflammation of a tendon, commonly caused by overuse or repetitive motions. In the case of the shoulder joint, this condition is called rotator cuff injury.
Step-by-step explanation:
Tendinitis is the inflammation of a tendon, which is the thick band of fibrous connective tissue that attaches a muscle to a bone. It commonly occurs when a tendon is over-extended or worked too hard without rest.
The tendons surrounding the shoulder joint can become inflamed due to repetitive motions over time, such as those performed by baseball pitchers when they throw a fast pitch overhead. This condition is called rotator cuff injury.