"Although called tennis elbow, lateral epicondylitis is much more commonly seen in people who are over using their arm doing something else. It could equally well be called "plasterer's elbow" or "mechanic's elbow" or "painter's elbow".
The most common cause is over use
of the muscles which are attached to the bone at this part of the elbow. That is to say, the muscles which pull the hand backwards (the wrist extensors). All the extensor muscles of the hand attach to the elbow at the outer part (the lateral epicondyle). If they are strained or over used they become inflamed, which means they are swollen, painful and tender to touch.
Sometimes the inflammation is caused by a direct injury or bang. Sometimes, especially when the cause is direct injury or strain, the muscles are actually partially torn.
Rarely the inflammation comes on without any definite cause, and this may be due to an arthritis, rheumatism or gout. Sometimes the problem is partly or completely due to a neck problem, which is causing pain in the elbow via the nerves from the neck."