How does the elbow medical and lateral epicondylitis?

Lateral epicondylitis, or “tennis elbow,” is an inflammation of the tendons that join the forearm muscles on the outside of the elbow. The bony bump on the outside (lateral side) of the elbow is called the lateral epicondyle. The ECRB muscle and tendon is usually involved in tennis elbow. 
Medial epicondylitis, or “golfer’s elbow,” is an inflammation of the tendons that attach your forearm muscles to the inside of the bone at your elbow. It's identified by pain from the elbow to the wrist on the inside (medial side) of the elbow. The pain is caused by damage to the tendons that bend the wrist toward the palm.