Elbow Dysplasia

What is canine elbow dysplasia?

The word “dysplasia” means “abnormality of development”. The elbow is a complex joint because it involves the articulation of three bones. If the three bones do not fit together absolutely perfectly as a result of abnormal development, the consequence is abnormal concentration of forces on a specific region of the elbow joint. Forms of primary cartilage disease may also constitute abnormal development. The term “Developmental Elbow Diseases” may be a more descriptive nomenclature for this condition since most people will have heard of “dysplasia” only in reference to the hip joint, and elbow dysplasia has little in common with hip dysplasia. Furthermore, the term elbow dysplasia intimates a discrete entity, when in fact there are many forms of developmental elbow diseases, which have very different causes and treatments.

How can I tell if my dog has elbow dysplasia?

Elbow dysplasia is the commonest cause of fore limb lameness in young large and giant breed dogs. Most dogs have a limp on one or both front legs. This can be seen as a nodding of the head when the good leg is placed and lifting of the head when the bad leg is placed. Some dogs that limp on both front legs will not have a limp, but will have an unusual “paddling” gait. Lameness is often triggered by exercise, although many dogs will exercise freely and limp afterwards. Although most dogs will be diagnosed before they are 2 years old, some dogs will not limp until they are older. Collectively, elbow dysplasia and elbow osteoarthritis are the commonest causes of fore limb lameness in dogs of any age. Small dogs can also be affected by elbow dysplasia, and this problem should be suspected in any dog with fore limb lameness that has not been caused by trauma.

What is the cause of elbow dysplasia?

This condition is primarily of genetic cause, although environmental factors such as obesity during puppyhood may influence whether an animal with the genes coding for elbow dysplasia will develop a clinical problem. Current estimates state that more than one hundred genes code for elbow dysplasia. Our ultimate goal will be to genetically map affected animals and tailor breeding programmes to minimise this disease.

Figure 1: This image shows the pattern of stress fracture radiating from part of the coronoid process of the ulna.
Picture 2: This is a microscopic image of a crack forming beneath the surface before it is visible at the surface. Fitzpatrick Referrals were responsible for the landmark research that showed that medial coronoid disease began in the bone beneath the surface and was not primarily a disease of cartilage.

What is happening inside an affected joint?

There are several different disease processes that are collectively termed elbow dysplasia. In most affected dogs, the pathology involves concentration of abnormal forces on a part of the joint called the coronoid process of the ulna. These abnormal forces cause microscopic stress fractures within this process, resulting in pain and lameness. In many dogs, either a small portion of the process, or the entire process will separate from the remaining bone. This problem is called fragmented coronoid process (FCP). Whilst
standard radiographs are very helpful in diagnosis of this condition, CT and MRI scans can provide more specific information regarding “fit” of the bones and ultimately only arthroscopy (keyhole examination) can provide all the information regarding the joint surfaces which will allow efficacious treatment.

The pattern of abnormal development is not the same in all affected elbow joints. In order to offer the optimal treatment for a dog with elbow dysplasia, it is essential that we identify and neutralize the abnormal forces acting on the affected elbow. These forces are summarised below: