Epicondylitis is a painful or tender condition on the outer part of the elbow the “epicondylus lateralis humeri”.
The area around the epicondylus is supplied by the nerve cutanaeus brachii lateralis inferior. It is a branch of the radialis nerve, which arises in the middle of the upper arm, and pierces the lateral head of the triceps muscle. If the muscle is tight, the nerve gets compressed, and a sharp pain at the area of the nerve supply, on the outer side of the elbow, called “tennis elbow”, occurs.
In some cases inflammation of the origin of the common extensor tendon causes similar symptoms.