The elbow joint is surrounded by muscles that move your elbow, wrist and fingers. Tendons connect some of these muscles to the bony prominences in your elbow. When your muscles and tendons are overloaded, tiny tears can form and cause the tendons to thicken. Over time, this can become painful and restrict movement.
As the name suggests, it can be caused by repetitive exercises, such as playing tennis or golf. However, it's often caused by other activities that place repeated stress on the elbow joint, such as computer use, decorating, playing a musical instrument, weight training or by forceful, repetitive movements at work. It’s especially common if you work in carpentry, construction or plumbing. Pain on the outer side of the elbow is often known as tennis elbow (lateral epicondylitis) and pain on the inner side of the elbow is referred to as golfer's elbow (medial epicondylitis).