Degenerative joint disease (DJD) is a non infectious form of arthritis that manifests as joint pain and reduced function. It is the most common form of arthritis seen in veterinary patients. DJD can be primary (old age change) or secondary to trauma, instability or developmental orthopedic diseases. Secondary DJD is the most common presentation. Abnormal stresses placed on normal cartilage or normal stress on abnormal cartilage can start the degenerative inflammatory process. The outer surface of the cartilage which is normally smooth begins to roughen and small cracks or fibrillations develop in the cartilage. The fissures can deepen to the level of the underlying bone. Exposure of the cartilage matrix incites an inflammatory response in the joint which degrades the cartilage further. The weakened cartilage is further susceptible to mechanical damage during weight bearing. Thus a vicious cycle ensues of cartilage breakdown and inflammation. The results are cartilage loss, subchondral bone thickening, new bone formation near joint capsule and ligament attachments (osteophytes), soft tissue fibrosis and pain. Due to the lack of blood vessels in cartilage, normal cartilage receives its nutrition from the surrounding joint fluid. Therefore, when cartilage is damaged it is slow to heal and is usually replaced by substitute fibrocartilage, which is inferior to articular cartilage.
Conditions which may cause DJD include OCD, joint fractures, joint luxations, ligament ruptures, elbow dysplasia, hip dysplasia, aseptic necrosis of the femoral head, patella luxation, premature closure of growth plates or infectious arthropathies.
Clinical signs usually include stiffness, which is worse when first rising or after exercise. Various degrees of lameness may be seen depending on the cause. With time the joint is often thickened and the normal range of motion is reduced. Manipulation of the joint may reveal crepitus (bone to bone grinding), pain or instability. Diagnosis is usually based on an orthopedic exam and radiographs.
Treatment of DJD is best directed at the underlying cause when possible and is based on severity of clinical signs or the potential for worsening of clinical signs in the future. Treatment may be medical or surgical depending on the underlying cause. Medical management of DJD is usually symptomatic and may be used as a sole form of therapy or after surgery. The components of medical management are weight management, controlled exercise, anti-inflammatory medications and nutritional chondroprotectants.
Weight management is crucial for the successful treatment of DJD. Obesity may be a causative or perpetuating factor in the problem. Weight loss often results in diminished pain, makes exercise easier and eases the burden on painful joints. Controlled exercise is useful for maintaining joint mobililty, increasing muscle mass and joint support. Activities should be chosen that allow full range of motion over sustained periods of time while minimizing pounding or stop and go activities. Anti-inflammatory medications provide pain relief and decrease the inflammation within the joint. We commonly use Carprofen, Etodolac and buffered aspirin in our patients. These medications and others in the non-steroidal class are most beneficial in the initial treatment of DJD to decrease the inflammatory response in the joint. If used on a prolonged basis they do have potential side effects (GI upset and ulceration most commonly) so we would prefer not to have patients taking these drugs for long periods of time. Cortisone or corticosteroids are powerful anti-inflammatories, however they are associated with significant side effects including cartilage damage when used chronically and are not recommended. There are a variety of nutriceutical or chondroprotective agents currently available for veterinary patients. These include glucosamine, chondroitin sulfate, and hyaluronic acid. Most incorporate the building blocks of normal articular cartilage with the goal of replacing damaged cartilage components. These are generally slow acting medications that require time to be effective in improving joint health. Some patients respond very well to these drugs while others seem to have no improvement.
Surgery is often used to treat the underlying cause of DJD. Examples include stabilization of a knee with a cruciate rupture with a tibial plateau leveling osteotomy (TPLO), fixation of an articular fracture, a total hip replacement or a femoral head and neck ostectomy (FHO) for hip dysplasia. It is important to note that DJD present at the time of surgery is not reversible and in most cases continues to progress after surgery. Often the goal of surgery is to minimize this progression.
