What are the causes of elbow pain?

Causes of elbow pain

• Lateral humeral epicondylitis (caused by traumatic 'tennis elbow or Spondyloarthritis -related enthesitis): Pain & tenderness over the lateral epicondyle. Radiation of pain to the extensor forearm. Pain reproduced by resisted active wrist extension with the elbow extended or supination of the forearm with the elbow extended.
• Medial humeral epicondylitis (caused by traumatic 'golfer's elbow or Spondyloarthritis -related enthesitis): Pain & tenderness over the medial epicondyle. Radiation of pain to the flexor forearm. Pain reproduced by resisted active wrist flexion and pronation of the forearm.
• Olecranon bursitis (caused by gout, rheumatoid arthritis or infective, as in tuberculosis): Pain over the olecranon. There may be a tender swelling. 

The intra-articular injection site in case of tennis elbow:

[Source: Davidson's principles and practice of medicine 23rd Edition; page 998 and image is taken from Kumar & Clark’s Clinical Medicine 9th Edition (2016) Figure no. 18.5]