By JOHN T. PAYNE DVM, MS
Osteoarthritis is a chronic, incurable disease of joints that is characterized by joint instability, and loss of articular cartilage. Clinically, osteoarthritis causes varying degrees of pain and dysfunction. Osteoarthritis generally is characterized as primary or secondary. Primary osteoarthritis is old age wear and tear arthritis and while common in humans, is uncommon in dogs. Secondary arthritis is common in dogs and is a response to a joint injury of some type. The most common causes of secondary osteoarthritis in dogs include hip and elbow dysplasia, cranial cruciate ligament ruptures, osteochondritis dissicans of various joints, patellar luxation and joint trauma. All of these conditions cause instability or abnormal weight bearing of joints leading to loss of articular cartilage, joint instability and periarticular osteophyte (bone spur) formation.
Osteoarthritis begins with an insult to the joint that causes damage to the articular cartilage. Once the cartilage is damaged, the injured cartilage cells release chemical mediators into the joint fluid that are engulfed by the synovial cells (lining cells of the joint capsule). The synoviocytes release a number of different cellular messenger chemicals that circulate back to the cartilage cells that cause further damage to the cartilage cells. This vicious circle continues its cycle leading to escalating damage to the joint and causing pain to the patient.
Diagnosis of osteoarthritis in dogs is generally based upon physical examination and diagnostic testing. Physical examination will often show gait abnormalities such as lameness and examination of affected joints often shows pain on manipulation, limited range of motion, joint effusion (excessive fluid in the joint), and joint enlargement caused by excessive scar tissue formed in an attempt by the joint to stabilize itself. Radiographs of affected joints will demonstrate osteophyte formation (bone spurs) , soft tissue swelling, and remodeling of the bones on both sides of the joint. Blood work generally is normal and not helpful in making the diagnosis. Other laboratory tests such as joint fluid analysis, infectious disease titers, and advanced imaging (CT ort MRI scans) may be recommended to rule out other causes of arthritis such as immune-mediated disease and tick-borne illnesses.
Treatment of osteoarthritis may take many forms. Generally, treatments fall into the categories of medical, surgical or alternative therapies. In most dogs, more than one type of therapy may be needed to alleviate the clinical signs of pain and lameness.
Surgical therapy is often used when there is a surgically correctable cause that is causing the osteoarthritis. It is often impossible to make a dog comfortable that has an unstable joint. Typically, if a ligament injury such as a cranial cruciate ligament injury or collateral ligament injury is identified, the first step in treating the joint disease is to surgically stabilize the joint. This often leads to rapid relief of pain and a slowing of the joint deterioration. Following surgery, medical management may be needed either on a temporary or permanent basis to make the patient is comfortable as possible.
Medical therapy is used to achieve symptomatic relief in patients with joint pain secondary to osteoarthritis. Medical therapy may take many forms and may involve weight loss, Non- Steroidal Anti-inflammatory Drugs (NSAIDs), physical therapy, and nutritional supplements.
Weight loss is often the most important therapy in dogs with osteoarthritis. Obesity in dogs is at epidemic proportions and leads to mechanical overload of the joints and makes other therapies far less effective. Weight loss in dogs requires a diligent and cooperative owner and considerable time investment, and depends on calorie reduction in the diet and increases in exercise to burn calories. In some dogs, weight loss medications such as Slentrol may help with weight loss since dogs on this medication may be less likely to beg and annoy the owners.
NSAIDs are the centerpiece of any osteoarthritis treatment plan and are by far the most effective medications used. NSAIDs are effective both by reducing joint pain and by reducing joint inflammation and may be used daily on a long term basis or may be used temporarily on an as-needed basis. Although generally safe for long term use, NSAIDs can cause serious side effects such as gastric ulceration and liver damage and blood work should be monitored periodically to make sure that dogs are tolerating the medications well.
Physical therapy to help maintain joint range of motion and maintain muscle strength is helpful in the therapy of OA since good muscle tone helps to maintain joint stability and good range of motion is helpful in maintaining normal gait. Nutritional supplements such as glucosamine, chondroitin sulfate, and omega III fatty acids (fish oil) are also helpful and act as general systemic anti-inflammatory medications. Even though effective, it is important to recognize that these supplements have low potency and are often not effective as a sole form of therapy.
Alternative therapies are popular therapies but it must be kept in mind that alternative therapies generally are not proven to be effective in the medical literature. Therapies such as cold laser therapy, stem cell therapy, chiropractic and homeopathy are available but have little controlled study proof of efficacy. The wise consumer should recognize that these therapies all require continued study to see where or if they fit into the armamentarium of osteoarthritis treatments.
John T. Payne DVM, MS
Diplomate, American College of Veterinary Surgeons
Pittsburgh Veterinary Specialty and Emergency Center
Department of Surgery
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