This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
Between the skin covering the olecranon process and the bone is a bursa, which, from its exposed position, is not infrequently diseased. It lies in the subcutaneous tissue and resembles in all respects the bursa in front of the patella. In those whose occupation causes them to rest frequently on the elbow, this bursa becomes enlarged, hence the name " miner's elbow." The bursa lies on the posterior surface of the bone and extends from the tip of the olecranon downward in the direction of the forearm. Excision is the most efficient treatment. There are no dangerous structures to be encountered in the operation because the bursa does not communicate with the joint. The position of the ulnar nerve should be borne in mind. It can readily be avoided and usually is not seen. There is sometimes another bursa on the upper surface of the olecranon just below the insertion of the triceps. It is rarely affected.