suffering from Athritis?
Types of Arthritis
Facts about Arthritis
The most common form of canine arthritis is Osteoarthritis (OA). Osteoarthritis is also one of the most common causes of lameness in dogs. It is caused by a deterioration of joint cartilage, followed by pain and loss of range of motion of the joint. Cartilage is a smooth, resilient tissue that lines the joints, allowing nearly frictionless joint movement, and providing shock absorption. Disruption of cartilage leads to increased friction and inflammation in the joints. This erodes the bone and can cause formation of new bone, called osteophyte (bone spur) formation, which interferes with normal joint movement and can cause pain. Eventually, the joint cartilage can wear away to the point that the underlying bone, named subchondral bone, is actually grinding against the adjacent subchondral bone. Because subchondral bone is rich in nerve supply, having exposed subchondral bone is a main source of pain in dogs with OA. The hips may be the most commonly affected joint, due to the high prevalence of hip dysplasia in dogs. One study identified hip Osteoarthritis in 30% of German Shepherd dogs (Hedhammar et al., 1979). A survey of 100 dogs identified OA in 52% of hips, 37% of shoulders, 36% of stifles (knees), and 5% of elbow joint. Osteoarthritis is more prevalent in overweight dogs than their non-overweight siblings.
Symptoms of Canine Osteoarthritis:
At a young age, the signs of OA are acute joint pain and lameness. This acute phase of OA is often ignored and OA is generally diagnosed later in life when its chronic signs become more significant. Many owners first notice that their dog seems stiff after vigorous activity or when the dog first gets up after resting for a period of time (for example, upon waking up in the morning). The dog will often warm out of stiffness when beginning an activity, but may refuse to perform strenuous activities altogether. Dogs may be reluctant to jump into the car or go down stairs, and may lag behind on walks, or may appear slow to rise. They may also seek warmth and soft, comfortable surfaces, and may lick or chew at the affected joint. Dogs do not normally cry when in pain, so it is important to recognize other signs of OA pain.
Predisposing causes for Canine Osteoarthritis:
OA can be caused by conditions that result in abnormal shape of joint surfaces, such as hip or elbow dysplasia (abnormal development) and patellar luxation (slipping of the kneecap to the side of the joint). Additionally, OA can result from trauma (for example, a fracture that leads into a joint or ligament damage resulting in an unstable joint). Two reports reviewing the outcome of management of fractures of the hip socket using bone plates identified OA in 72% to 85% of the patients. Unlike humans where OA is often primary, OA rarely develops without a known underlying cause in dogs.
Any condition that results in abnormal strain on the joint can predispose a dog to developing arthritis. Obesity has been proven to predispose dogs to arthritis and makes the disease progress faster in dogs that already have arthritis. Therefore, it makes sense to keep dogs slim. Further studies are needed to determine if obesity truly initiates OA in dogs; however, it is well known as a risk factor in humans.
How to Diagnosis:
Your veterinarian will diagnose your dog with arthritis using several different procedures. First, he or she will listen to you describe your dog’s symptoms, and then will conduct a complete physical and orthopedic examination. The vet may watch your dog move around, note the position in which your dog chooses to rest, and palpate (feel) the joints and their range of motion. Other diagnostic tests may include radiographs (x-rays) and arthrocentesis (sampling the joint fluid using a needle). Radiographs often show joint changes, but severity seen on x-rays often does not correlate well with the amount of pain a dog experiences. Some dogs may appear very painful but show little bony change on radiographs, while others may exhibit no symptoms, but have severe changes on radiographs. Other imaging techniques may include arthrography, (a contrast dye is injected into the joint that can be seen on x-ray), CT scan, or MRI, which is expensive but may provide the best imaging of the joint and can allow cartilage loss to be seen.
Canine Arthritis Treatment:
The goals of treatment are to eliminate the underlying cause of the arthritis (possibly with the use of surgery to stabilize or correct an abnormal joint), to reduce pain and inflammation, to improve joint function, and to slow or halt the arthritic process. Treatment can include both management as well as drug therapy.
Weight: It is important that the dog maintain a normal weight; obese dogs should be put on a strict diet. Lower weight leads to less stress on the joints, and this can help reduce the dose or frequency of drug administration, which, in turn, can reduce side effects.
Exercise modification: A controlled, moderate exercise program performed consistently is best. Moderate exercise can help maintain range of motion of the joint, maintain muscle mass, and promote cartilage health. Exercise also helps with weight reduction. The exercise level should be modified according to the needs of the individual dog. If the dog seems stiff following a certain amount of exercise, it should be slightly reduced during the next activity period.
Environmental modification: Ramps can help to reduce the painful activities like jumping into cars, or onto couches or beds. Small dogs can be carried up flights of stairs or during other uncomfortable activities.
Arthritis Medications: Never give your dog any medications, including human over-the-counter medications, without talking to your veterinarian. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most common drug category prescribed. Six are approved by the FDA for use in dogs: Rimadyl (carprofen), Deramaxx (deracoxib), Etogesic (etodolac), Metacam (meloxicam), Zubrin (tepoxalin), and Previcox (firocoxib). These drugs decrease pain and inflammation, and carprofen has even been shown to have some protective effects on cartilage. NSAIDs have several important side effects, for example, they can cause stomach ulceration, renal disease and, in rare cases, can cause liver damage, so should be used with care and at the lowest possible effective dose. Your veterinarian may monitor your dog’s bloodwork regularly to check for any signs of organ damage.
Corticosteroids like prednisone or dexamethasone are used rarely and only when NSAID therapy has not controlled the dog’s pain. These drugs provide excellent control of inflammation, but can delay healing and even initiate cartilage damage, and therefore are used only for a short period of time as a last resort.
Cartilage-protecting agents include polysulfated glygosaminoglycans (Adequan) and hyaluronic acid (Legend). Adequan is administered as an intramuscular injection. It may help decrease the amounts of enzymes that destroy cartilage and is said to stimulate cartilage growth. Little is known about the short-term and long-term benefits of Adequan in patients with chronic OA. Hyaluronic acid is injected directly into the joint. It is a natural component of joint fluid that can help lubricate the joint and may help to relieve pain. The benefits of hyaluronic acid in dogs with chronic OA are unknown.
Nutraceuticals, which are supplements not regulated by the FDA, include Cosequin (glucosamine and chondroitin), MSM, and many others. Cosequin provides some raw materials needed to synthetize cartilage. Anecdotally, Cosequin appears to show benefits in dogs with OA even though these benefits have not been assessed in a prospective randomized study and does not have any known side effects. MSM has not been well-studied but is sometimes used to help manage OA.
Fatty acids can also be a useful supplement. Omega-3 fatty acids may decrease inflammatory hormones, called prostaglandins, that can further contribute to joint damage. Several clinical trials confirmed the benefits of some omega-3 fatty acids in dogs with chronic OA.
Physical therapy may also help improve strength and range of motion and decrease discomfort.
If these factors do not adequately control pain, certain surgical procedures can be performed. For the hip joint, a common location of arthritis due to hip dysplasia, there are two main options: total hip replacement (THR) or femoral head ostectomy (FHO). The total hip replacement is an ideal, but costs 3 to 5 times as much as an FHO. THR is very similar to a hip replacement in humans. Both the socket as well as the ball are replaced. THR leads to excellent clinical results in large dogs, FHO generally does not. A femoral head ostectomy is a procedure in which the head of the femur (the “ball” at the top of the thighbone that fits into the hip “socket”) is removed, and a piece of muscle or joint tissue is placed between the socket and thighbone. This allows the scar tissue and surrounding muscles to support the leg, and completely eliminates the problematic joint. This surgery is best for smaller dogs, and is also often performed when owners cannot afford a total hip replacement, but is not as successful in large dogs.
Prevention: One of the most important causes of arthritis in dogs is hip dysplasia. Therefore, choose a breed that is not predisposed to this condition or at least a very reputable breeder. Additionally, keep your dog at a healthy weight and exercise him regularly at a reasonable level.
Authors: Elizabeth M. Lennon, BA, North Carolina State University Veterinary School, Raleigh, NC
Denis J. Marcellin-Little, DEDV, Diplomate ACVS, Diplomate ECVS, North Carolina State University Veterinary Hospital, Raleigh, NC