They do not themselves contract, but by exerting a firm hold on the muscles and bones, they help transform muscle contractions into movement.
Tendons are durable tissues, and normally they can withstand many years of use without any problems.
Not surprisingly, tendinitis generally occurs near the most heavily used joints of the body - those of the arms and legs. It is associated with particular athletic activities that give it a variety of popular names. When it occurs in the outer elbow, it is known as tennis elbow. In the inner elbow, it is known as golfer's elbow. When it occurs in the knee, it is jumper's knee.