This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
Tennis elbow', is characterized by - 
Select and explain. 
A. Tenderness over the medial epicondyle, B. Tendinits of common extensor origin, C. Tendinitis of common flexor origin, D. Painful flexion and extension
B: Tendinits of common extensor origin
Answer: B: Tendinits of common extensor origin 
Explanation: Tennis elbow is extraarticular affection characterized by pain and acute tenderness at the origin of the extensor muscles of the forearm from the lateral epicondyle.
It is believed to be caused by a strain of the forearm extensor muscles, particularly the extensor carpi radialis brevis, at the point of their origin from lateral epicondyle.