Degenerative Joint Disease ... Arthritis

Degenerative Joint Disease (degenerative arthritis) is a non-infectious, progressive disorder of the weight bearing joints. The normal articular joint cartilage is smooth, white and translucent. It is composed of cartilage cells (chondrocyte) imbedded in a sponge-like middle, or matrix, made of collagen, protein polysaccharides and water. With early, primary degenerative arthritis, the cartilage becomes yellow and opaque with localized areas of softening and roughening of the surfaces. As the degeneration progresses, the soft areas become cracked and worn exposing bone under the cartilage, which begins to remodel and increase in density while any remaining cartilage begins to fray. Eventually, osteophytes (spurs of new bone), covered by cartilage, form at the edge of the joint. Also, as mechanical wear increases, the cartilage needs repairing. The cartilage cells are unable to produce enough of the sponge-like matrix and therefore the damaged cartilage cannot repair itself. In fact, it has no blood supply to enhance healing.

The majority of degenerative joint disease is the result of mechanical instabilities or aging changes within the joint. This includes old age degenerative arthritis and, in younger animals, may be the result of injuries, bruises, abnormal joint configuration, (i.e. hip dysplasia), or mechanical wear from anterior cruciate ligament rupture (see Volume V/5 of The Mastiff Reporter), patellar luxation, or osteochondritis dissecans.

SYMPTOMS

In most cases, degenerative joint disease is seen in dogs midway through their life expectancy, with an increasing incidence in the older animal. The early signs are mild and include a slight decrease in physical activity with a history that the dog is stiff, "not as playful", and is reluctant to go "on long walks". As the condition progresses, the animal, depending on the joint or joints involved, may stand up slowly after lying down for a period of time, may walk up and down stairs more slowly or may be reluctant to jump up as usual upon household furniture. At this stage, the individual's stiffness will diminish as he/she moves about. This is referred to as warming out of the lameness. Eventually, he/she may be asymptomatic at some time during the course of the day, only to have the whole episode repeat itself the next time he/she gets up from a rest. As the disease progresses, the above-mentioned signs increase in severity to a point where the dog refuses to stand and walk. Cold, damp weather accentuates the clinical signs in most cases, not only because of the cold temperature, but also because of barometric changes.

RADIOGRAPHS (x-rays)

Because cartilage does not show on radiographs (x-rays), early degenerative joint disease may show only a narrowing of the joint space. As the disease progresses, bone spurs, or osteophytes, form and the bone under the cartilage becomes very hard.

TREATMENT

Treatment is limited to reducing the degree of pain present in the joint capsule and surrounding ligaments (the joint cartilage has no nerve endings) so that activity can continue and muscular support can be increased. The most important consideration in the long term treatment of arthritis is the Maintenance of Muscular Support.

As the arthritis progresses and pain worsens, aspirin (Ascriptin), or more potent drugs such as Phenylbutazone, may be required. Corticosteroids can be given, but because of potential side effects, should be used only after other drugs have been tried and found to be unsuccessful. (Ed. Note: New non-steroidal anti-inflammatory drugs have been developed by Pfizer Labs and Fort Dodge are potential candidates for treatment of these problems -- ask your vet if your pet would be a good candidate for use of Rimidyl (Pfizer) or Ecto-Gesic (Fort Dodge) for pain and arthritis). These drugs should allow one to maintain the animal on normal exercise levels of walking, jogging or swimming. Swimming is by far the best activity, as it allows maximum motion with minimal weight bearing. Strenuous exercise is contraindicated. Obese dogs should be put on a reducing diet. If surgery is performed on the affected joint, passive flexion and extension exercises will begin soon after bandage removal to "work out the stiffness". This will be followed by very light activity as the long road toward complete rehabilitation is begun.

Another treatment involves drugs that actually help heal the matrix of the damaged cartilage. These innovative drugs have revolutionized the treatment of arthritis when treatment begins before irreversible damage has been sustained.

INFECTIOUS ARTHRITIS

Infectious arthritis is the result of the penetration of living microorganisms into the synovial membrane (joint lining), or into the synovial membrane and joint cavity. The most common type of organism causing this problem is bacteria, usually Staphylococcus or Streptococcus.

Three basic causes of bacterial arthritis are:

1. a penetrating wound of a joint,
2. the presence of a bacteremia (blood stream infection) with localization in the joint,
3. the spread of infection from an adjacent osteomyelitis (bone infection).

The clinical signs are those of the basic inflammatory process: swelling, heat, and pain in the joint(s), and occasional redness of the overlying skin. One or more joints may be involved. The body temperature is often elevated, and the patient is lethargic, occasionally anorectic, resists movement of the joint, and is lame in the affected limb(s). The area should be examined closely for a penetrating wound.

A definitive diagnosis of infectious arthritis can be made only by isolating the infecting organism from the joint fluid or synovial tissue. Clinical history and signs, synovial fluid analysis (other than culture), and radiographic findings can help only to limit the possible causes of a painful joint.

(The preceding article was printed with permission of the Southern California Surgical Group in Irvine, California).