This is Tuberculosis of the elbow. (Unknown provenance.)
There is a focal area of bone destruction and irregular new compact bone affecting the entire distal end of the humerus. The whole of the distal end is covered in a mixture of irregular spiculated and nodular new compact bone with diffuse inflammatory pitting, especially on the posterior surface and in the olecranon fossa. There is ossification of the distal ligaments and muscles at their attachment sites. There is a cloaca on the superior border of the olecranon fossa. The extent of the bone destruction to the distal end is unknown due to taphonomic damage. However, there is evidence of extensive destructive change on the radial head and trochlea. There is an extension of new compact bone with inflammatory pitting to the midshaft of the posterior surface and laterally new compact bone at the site of the attachment of M. brachioradialis and a portion of M. triceps brachii (medial head).
Despite the extensive taphonomic damage, there is evidence that the superior quarter of the bone was covered in a thick layer of smooth compact bone with inflammatory pitting on most visible surfaces and areas with bony nodules of new compact bone. On the posterior surface of the neck there are two large destructive lesions that are probable cloacae.
There is irregular new compact bone with extensive inflammatory pitting on the superior end with enthesophytes at the attachment s of the superior ligaments and muscles, especially M. supinator and flexor M. carpi ulnaris anconeus. Spiculated new compact bone surrounds the radial articular surface. Although affected by taphonomic damage, evidence remains of partial bony destruction of the olecranon process.