Degenerative joint disease (DJD), or arthritis, affects the smooth articular cartilage of the joint, which is the covering of bone in the joints that is responsible for the smooth, non-painful motion of joints. When it becomes worn, raw bone surfaces become exposed and rub together. DJD is the result, causing pain and lack of joint mobility.
DJD can occur over a lifetime of wear or as a result of injury. The soft tissue lining of the joint (synovium) is the first tissue in many animals to be affected in the disease and the subsequent irritation of the joint lining (synovitis) liberates chemical mediators that have been shown to be responsible for cartilage degeneration.
Primary cartilage damage can also initiate a cascade of events that result in further cartilage damage and synovial lining inflammation. This results in a vicious cycle of cartilage degeneration, release of degenerative factors and continued cartilage degeneration.
Normal cartilage is composed of cartilage cells (chondrocytes) and a supporting substance (matrix) that is produced by the cells. DJD involves the derangement of chondrocyte metabolism and subsequent matrix alteration.
What to Watch For Lameness
Swollen joints
Muscle atrophy
Dry crackling sound upon movement of the joint (crepitation)
Diagnosis
Diagnostic tests are needed to recognize DJD and exclude other diseases. Tests may include:
Complete medical history and physical examination
A thorough orthopedic examination. DJD is usually characterized by a slow-onset, waxing and waning lameness pattern of the affected joint. Depending on the length and severity of the disease pain, swelling and grinding may be felt.
Radiographs (X-rays) of the suspected joints. These will show evidence of the degenerative process. If the DJD is secondary to a primary problem, evidence of the primary problem is frequently discovered. Occasionally the introduction of contrast material ("dye") into the joint (arthrogram) may uncover a primary problem. Advanced imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI) or bone scan (scintigraphy) is occasionally of diagnostic value.
Joint fluid analysis. This test can help differentiate between degenerative joint disease and other causes of more inflammatory joint disease, such as canine rheumatoid and infectious (bacterial, fungal etc.) arthritis.
Treatment
Treatment for DJD may include one or more of the following:
Medical treatment and weight reduction are often the initial hallmarks toward treatment of DJD. Weight reduction decreases stress placed on the joints and a number of older and newer drugs have been used to alleviate the clinical signs associated with DJD. Nonsteroidal anti-inflammatory drugs (NSAIDS) have been used for years since Bayer marketed acetylsalicylic acid (aspirin) in 1899. All drugs have potential side effects; however, the newer NSAIDs seem to have less side effects than aspirin in animals. Aspirin should not be used in cats. Corticosteroids (cortisone) decrease the inflammation of DJD, although it is a well-established scientific fact that chronic steroid use causes cartilage damage and should not be used for long-term therapy.
Surgical treatment of traumatic causes of secondary DJD (such as knee ligament rupture), seem to slow the progression of the degenerative process.
Either arthrodesis (fusion) or other arthroplasty (joint replacement or excision) procedures are usually very successful in restoring pain-free range of motion in selected cases of DJD.
Home Care and Prevention
After your cat's surgery, follow your veterinarian's specific instruction concerning medications, care and recheck examinations. Limited range of motion and physical therapy exercises are usually beneficial.
Since some of the developmental orthopedic conditions that result in DJD have some component of inheritability, selective breeding of unaffected animals will help decrease the incidence of the disease in the population as a whole. This can decrease the incidence of many of the congenital orthopedic problems.
Proper nutrition is also important in order to have a normal weight gain during development. Over-nutrition and over-supplementation can lead to an increased incidence of hip dysplasia and other development orthopedic diseases in large breed puppies.
