Depending upon whom you talk to, the terms 'arthritis,' 'osteoarthritis' and 'degenerative joint disease' may or may not be used to describe the same thing. In this discussion, we will use the terms interchangeably.
What is degenerative joint disease (DJD)?
Degenerative joint disease is characterized by the loss of the smooth cartilage that covers and protects the end of the bones in a movable (synovial) joint. The cartilage has no nerves so when it touches the cartilage of another bone, there is no pain. When the cartilage wears away, the bone is exposed. The bone does have nerves so when the two bone ends in a joint touch each other it results in pain and inflammation - signals that arthritis is present. In degenerative joint disease we also see small bony projections (osteophytes) form on the bone that is close to the joint. This adds to the pain. This type of arthritis is progressive, meaning it continues to get worse.
What causes degenerative joint disease?
Degenerative joint disease can occur as a result of wear and tear on an otherwise normal joint and occurs as the cat ages. This is called primary degenerative joint disease. Osteoarthritis may also occur as a result of another condition affecting the joint such as hip dysplasia. Then it is called secondary degenerative joint disease.
Which cats are at risk of developing degenerative joint disease?
Certainly any cat with a congenital joint problem, like dysplasia is going to be more prone to developing degenerative joint disease. Cats who have had injury to a joint such as a fracture involving the joint will be more likely to develop arthritis.
What are the symptoms of degenerative joint disease?
The symptoms of arthritis will vary as to which joints are involved, the age of the cat and the severity of the disease. In general, the first symptoms may be an altered gait since the cat will try to put more of her weight on the unaffected limbs. There may be muscle atrophy (reduction in the size of the muscle) in the affected limb because the cat is using it less, or at least putting less weight on it. For instance, in a cat with arthritis in the hind legs, the muscles of the hind limbs may be thin, whereas, the muscles of the chest and shoulders may be increased in size because the cat is putting more weight on the front legs.
Many times the cat may find it difficult to get up after lying down and appears stiff. Cats with DJD may be unable to jump up onto a chair or windowsill. Many cats find it difficult to go up or down stairs.
Depending upon the amount of pain the cat is experiencing from the osteoarthritis, there may be changes in appetite and behavior (e.g., the cat may go off by herself more often). The joints are generally not swollen and the pain is the dull aching type, so cats do not often vocalize or cry out in pain. Some cats will lick or bite at the area that is painful. Some will seek out warmth or soft places to sleep.
How is degenerative joint disease diagnosed?
The veterinarian will obtain a good history of the cat's signs from the owner and perform a complete physical exam. Radiographs (x-rays) are taken, and further laboratory tests or more detailed exams of the affected joint(s) may be performed.
How is degenerative joint disease treated?
Degenerative joint disease can be treated medically and surgically.
What is the prognosis for cats with degenerative joint disease?
Degenerative joint disease is progressive - it will continue to worsen. There are ways we can medically treat the disease to slow down the progression and many cats respond well and can live comfortably for years. In more severe cases, surgery may be performed including actual joint replacements. In these cases, the recovery is usually very good.