2-Year-Old Neutered Male Mixed Breed

Signalment & History

  • This patient presents to your clinic for an intermittent lame on his right forelimb. His lameness presents after periods of resting or jumping and only persists for a few minutes before he is back to walking normally.
  • You order right elbow radiographs.



  • There is a large lucent gap between the anconeal process and the olecranon


  • This patient is diagnosed with ununited anconeal process
  • Additionally, there is an elbow incongruence with the radius being longer than the ulna


  • Thrall DE. Orthopedic diseases of young and growing dogs and cats. In: Thrall DE, ed. Textbook of veterinary diagnostic radiology. 6th ed. St Louis: Elsevier Health Science, 2013;268.
  • Co-existence of ununited anconeal process and fragmented medial coronoid process of the ulna in the dog. JSAP (2006) 47, 61-65.

Elbow dysplasia

Elbow dysplasia is a nonspecific term referring to a triad of developmental lesions that include ununited anconeal process, fragmented medial coronoid process of the ulna, and osteochondrosis of the distomedial aspect of the humeral trochlea. Abnormal contact between articular surfaces caused by incongruence of the elbow joint may result in nonuniform contact, leading to nonunion of the anconeal process or separation or fragmentation of the medial coronoid process.

Ununited anconeal process

A number of breeds including German shepherd dogs, Greyhounds, Pitbull Terriers, Golden Retrievers, and Labrador Retrievers, are known to have a separate center of ossification at the anconeal process. This is typically small and poorly defined with incomplete and irregular separation from the olecranon process. Dogs with a separate center of ossification do not always develop an ununited anconeal process, and the two should not be confused with each other.

Breeds at greatest risk include Bernese mountain dogs, mastiffs, Rottweilers, and Saint Bernards, although other large-breed dogs are also at risk.

Radiographic signs of Ununited anconeal process

The primary radiographic finding is best seen on the lateral view and consists of a radiolucent line separating the anconeal process from the olecranon in dogs older than 150 days. This lucent line can be sharply defined, or it may appear irregular and of variable width. Degenerative joint disease of the elbow is a common sequel, and periarticular new bone production from osteoarthrosis may partially obscure the lucency between the ulna and the anconeal process. A flexed lateral radiograph in addition to routine lateral and craniocaudal views of the elbow should be included in the radiographic examination.