Why does my elbow hurt when I bend and straighten it?

Tennis elbow, also known as lateral epicondylitis, is an inflammation accompanied by pain in the elbow joint. This is caused due to overuse or repetitive stress. The location of this pain is on the outside of the elbow or the lateral side. But eventually, the pain might radiate down the back of the forearm. This pain is usually felt when the arm is stretched or extended.