ELBOW DYSPLASIA

Elbow dysplasia is a disease with a high inherited component, which primarily affects intermediate and large breed dogs.    A high incidence of occurrence has been noted in the Bernese Mountain Dog, German Shepherd, Rottweiler, Golden  Retriever, and Labrador Retriever.  Some of the other breeds affected are the  Newfoundland, Saint Bernard, Mastiff, Springer Spaniel, Australian  Shepherd, Chow Chow, Shar-Pei, Shetland Sheepdog, and some Terrier  Breeds.   Typically, both elbows are affected. However, unilateral elbow  dysplasia is not uncommon.

DEVELOPMENT 

The elbow joint is composed of three bones (radius, ulna, and humerus) which must all grow together and fit perfectly. The radius and ulna are paired bones with the radius being the main weight bearing bone. The normal elbow joint is characterized by a smooth transition from the ulnar articular surface  to the radial surface.  In a dysplastic elbow the edge of the ulnar surface lies above the level of the adjoining radius, creating a step between the radius and ulna and causing incongruity of the joint.  The height of the step may vary from barely noticeable to 4 mm or more. When this occurs the weight bearing force on the ulna is increased, resulting in excessive pressure on the medial coronoid process.   This leads to fragmentation of the coronoid process. This usually occurs between 5 and 7 months of age.   A superficial to deeply grooved "kissing lesion" is often present on the  humeral articular surface opposite the fragment.   A cartilage flap  or OCD (osteochondritis dissecans) lesion may also develop. Secondary arthritis becomes evident at 6-7 months. Compensatory adjustments during  growth may occur in some dogs, tending to minimize unequal growth rates  between the three bones and moving the ulna distally   to better conform to the radius. . However, excessive force is then placed on the anconeal process at the top of the ulnar articular surface. This force will cause a  failure of ossification, leading to an ununited anconeal process.                                   

CLINICAL SIGNS 

 Affected dogs are frequently lame or have an abnormal gait. The gait is often characterized by excessive paddling or flipping of the front feet.   The animal may either hold the elbows out or tucked in and often stands  with the feet rotated outward. Many sit or lie down much of the time,     or play for shorter periods of time than other dogs of comparable age. They are often described as quiet or even lazy. Frequently, they are stiff when rising and tire easily.  Exercise typically  makes the lameness worse. In dogs with bilateral elbow dysplasia, the lameness may seem intermittent or shift from one front leg to the other. When both front legs hurt, dogs do not limp constantly. Rather, they shift weight off their elbows by altering their gait and stance. These dogs will only "limp" when one elbow is more painful than the other. On examination, manipulation of   the elbow is often resisted. Swelling and crepitus (grating) may be palpated. The  swelling may    be worse after exercise. In some cases, the joint will be thickened. Muscle atrophy may also be present.

DIAGNOSIS 

The routine monitoring for the presence of elbow dysplasia is  carried out from a lateral x-ray of  the flexed elbow joint taken when the dog is over 12monthsof age. Correct radiograph technique is critical for making the diagnosis.  The grade is derived by measuring the amount of new bone that has developed as a result of arthritis.  Unlike the grading systems for hip dysplasia the system for elbow dysplasia is used internationally.            

 ADVICE 

It is generally considered that dogs with grade 3 elbow dysplasia should not be used for breeding and that dogs with grade 2 should be considered a serious risk.

Re-worded by Prof. Bob Wyburn (BVMS, DVR, PhD, FACVSc, MRCVS)

 Reference:                        World Small Animal Veterinary Association