A person with lateral epicondylitis has inflammation of the lateral epicondyle. The lateral epicondyle is part of the humerus bone, near the elbow.

Tendons attach the muscles of the forearm to the lateral epicondyle. Strenuous use of the forearm muscles can cause inflammation of the bone where the tendons attach to the lateral epicondyle. Most cases of lateral epicondylitis resolve over 4-6 weeks with treatment and rest.