The most common cause of front leg lameness in the dog is developmental problems of the elbow joint. This disease leads to degenerative changes (osteoarthritis) in the joint including carti- lage damage, bone spur (osteophyte) pro- duction, and loose bone fragments.
ELBOW JOINT FUNCTION
The elbow joint of the dog is formed by three bones (the humerus, ra- dius and ulna bones {Figure 1}) that must fit together correctly for the joint to func- tion normally. There are ligaments on the inside and outside of the elbow to main- tain stability. Although the elbow joints of dogs and humans have similar anatomy, the forces applied to the dog’s elbow are different because dogs stand on their front legs. The humerus bone should glide smoothly around the C-shaped curve formed by the radius and ulna bones.
CAUSES OF ELBOW DYSPLASIA
Elbow dysplasia is typically a developmental, inherited disease of young large -breed dogs. In some dogs, during growth, a step develops in the C-shape between the radius and ulna bones possibly due to the radius bone being too short or too long relative to the ulna. This causes extra stress to be placed on prominent parts of the ulna bone (the anconeal or coronoid processes {Figure 2}) or the cartilage of the humerus. Cracks can then occur in the bone across the lines of greatest stress or the bone fails to grow normally. The joint cartilage may also be damaged in this process. Arthritis develops as a result of the damage to the bone and the cartilage.
There are three main forms of elbow dys- plasia that cause pain and arthritis:
- Fragmented coronoid process (FCP). A crack occurs in this triangular- shaped bony bulge on the inside edge of the ulna bone.
- Ununited anconeal process (UAP). A lack of normal bone growth re- sults in this bone fragment becoming loose at the top of the ulna bone.
- Osteochondritis of the humerus (OCD). A flap of loose cartilage develops on the inside surface of the humerus bone.
SYMPTONS
Typically, affected dogs show front leg lameness that can start as young as 5 months of age. The lameness may be in- termittent and tends to improve with rest and get worse with exercise. Not all dogs with elbow dysplasia show symptoms.
DIAGNOSIS
A thorough orthopaedic and neuro- logic examination is performed evaluating the dog when walking and by manipulating all four limbs and the spine. Swelling, pain, and joint stiffness can frequently be felt in the affected elbow. Sedation or anaesthe- sia and X-rays are necessary to show signs of arthritis and to assess the bone structure. A CT scan will often be more effective in showing any bony changes.
MEDICAL TREATMENT
Some dogs with confirmed elbow dysplasia will improve without surgery. The object of medical treatment is to control the symptoms. The dog should not be allowed to get overweight and ex- ercise should be controlled. Cartilage- protecting agents (omega fatty acids, glu- cosamine, green-lipped mussel, fish oil) may help lubricate the joint and keep cartilage healthy. Generally, lifelong supplementation is necessary. Anti-inflammatory medication (aspirin-like drugs) can be helpful in reducing pain but should only be necessary occasionally. Medical treatment does not stop arthritis from continuing to develop.
SURGERY
Other dogs with elbow dysplasia benefit from surgery depending on the type of damage and arthritis. The type of surgery differs from dog to dog and may involve passing a small telescope (arthroscope) into the joint to see if a step is present between the radius and ulna bones. Loose bone fragments may then be removed or stabilized using a bone screw. (Figure 3) The ulna bone may be cut to remove the step and a pin may be placed to help healing. (Figure 4)
RESULTS
Dogs that have had surgery generally show excellent results with some progression of arthritis, few complications and normal function. If the ulna bone is cut, healing takes about 2-3 months and most dogs can return to full activity 4-5 months after surgery.
Be sure to check out our article on post operative care for dogs with elbow dysplasia for best results post operation.