Symptoms associated with tennis elbow include, but are not limited to: radiating pain from the outside of the elbow to the forearm and wrist, pain during extension of wrist, weakness of the forearm, a painful grip while shaking hands or torquing a doorknob, and not being able to hold relatively heavy items in the hand. The pain is similar to the condition known as golfer’s elbow, but the latter occurs at the medial side of the elbow.
Tennis elbow is a type of repetitive strain injury, resulting from tendon overuse and failed healing of the tendon. In addition, the extensor carpi radialis brevis muscle plays a key role.
It has also been known that incorrectly playing tennis may cause early stages of tennis elbow as shock is received when mishitting the ball.
Source NHS Choices