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The Definitive Guide to Canine Joint Dysplasias

Dr. Sarah Wooten, DVM

Doctor of Veterinary Medicine

Westridge Animal Hospital

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What are Joint Dysplasias, Anyway?

Joint dysplasia is defined as disease that causes an articular joint, like an elbow or a hip, to develop abnormally, causing pain, loss of function, and arthritis. Joint dysplasias affect both bone and cartilage in growing dogs. Joint dysplasia is considered to be a developmental disorder that has a genetic component, and can be made worse by improper nutrition or exercise. Joint dysplasia is a serious condition that is unfortunately common in dogs.

In the dog, there are three joint dysplasia conditions:

Hip and elbow dysplasia are the most common joint conditions seen in dogs. Some orthopedic researchers also believe that cranial cruciate ligament disease could also be a developmental disorder, but there is no definite research in this area as of writing. To learn more, visit the definitive guide to cranial cruciate disease. In hip and elbow dysplasia, the joint develops a malformation as the dog’s skeleton grows, resulting in arthritis in the elbow or hip.

What Is Hip Dysplasia?

X-Ray of a Dog With Hip Dysplasia

What Causes Hip Dysplasia?

The hip joint is the connection between the head of the femur bone and the pelvis. The hip joint is a ball and socket joint that allows movement for walking and running. Normally, the joint is very stable and strong; however, dysplastic hip joints are weaker due to malformation of the ball and socket.

The hip is the joint most commonly affected by osteoarthritis in dogs. While traumatic causes such as hip subluxations and hip fractures can also cause arthritis, more commonly arthritis in the hip joint of the dog is caused by hip dysplasia.

Hip dysplasia is one of the most common skeletal diseases in dogs. Large breed dogs, such as German Shepherds, Labrador Retrievers, Golden Retrievers, Rottweilers, and Saint Bernards are more often affected. Hip dysplasia is a genetic, heritable disease, so any dogs that are diagnosed with hip dysplasia should not be bred. It is important to note that smaller dogs can also develop hip dysplasia, but they are less likely to show signs of disease.

While the exact genetic defects are not known, the main culprits of hip dysplasia are laxity (looseness) in the joint, and abnormal shapes of the bones that make up the ball and socket hip joint. In hip dysplasia, poor congruence, or poor ‘fit’ between the femoral head (the ball) and the acetabulum of the pelvis (the socket) creates abnormal forces across the joint, interfering with normal development and growth and leading to irregularly shaped surfaces. As the dog walks or runs, the head of the femur rubs abnormally on the cartilage of the pelvis, causing micro-tears in the joint cartilage. If the joint is loose, the hip joint can also pop out, subluxating and causing pain and limping.

Hip Dysplasia can start when a dog is very young. Dogs as young as 4 months of age can demonstrate problems with hip dysplasia. The signs of hip dysplasia depend on the severity of disease.

Hip dysplasia is a two-part disease. In very young dogs, pain is associated with subluxation of the joint. A subluxated hip joint is extremely painful as it causes tearing and stretching of the soft tissues associated with the hip joint. Over time, the joint can “scar down,” reducing the pain and subsequently the signs associated with hip dysplasia. As young dogs grow, they can appear to be improve, even with severe disease.

The second phase of hip dysplasia involves arthritis of the joint. Even though the joint is no longer subluxating, the joint abnormally flattens and over time wears down cartilage, causing pain associated with arthritis.

The tricky part with hip dysplasia is that the disease doesn’t always play by the rules. A dog that has terrible hip dysplasia as seen on X-rays may not display any signs or pain. Conversely, dogs that have minimal changes on X-ray can be very painful. Some dogs will only be painful as puppies, then never show signs again. More commonly, dogs will skip the puppy stage of the disease and show signs associated with arthritis pain later in life.

Hip Dysplasia: Signs and Symptoms

Dogs with hip dysplasia or hip arthritis may exhibit the following signs:

Whatever the age of your dog, if he or she is showing any of these signs, or a combination thereof, it is important to have your dog evaluated by a veterinarian.

Hip Dysplasia: What To Expect at the Veterinary Office

Your vet will most likely check your dog's neurological reflexes

During a veterinary visit, your veterinarian will take a history from you and do a full examination of your dog. This will usually include you walking and trotting your dog around so the veterinarian can assess your dog’s ‘gait’. Your veterinarian will then feel all the bones, muscles, and joints. They will test for pain. They will move joints through their range of motion while feeling the joint for any swelling or crepitus. Then your vet will most likely check neurological reflexes as well. When there is thickening, arthritis or degenerative changes around a joint, your dog will show fairly predictable patterns with each joint.

Your veterinarian will feel for muscle mass on your dog while he or she is standing and compare muscles on each side. Arthritis anywhere in a leg will cause loss of muscle mass over the entire leg, not just around the affected joint. Just because your pet has a bony hip does not automatically mean your pet has hip pain: it could also be knee or ankle pain. Also: loss of muscle mass can also be secondary to spinal or nerve dysfunction. Your veterinarian will determine whether the condition is musculoskeletal or neurological.

In young dogs, your veterinarian check for an Ortolani Sign, a test that checks for subluxation of the hip joint. Depending on your dog’s level of pain and comfort, this test may need to be performed under sedation.

One thing to be aware of is that some dogs with hip arthritis can also have muscle gain. Dogs with long-standing arthritis in the hind legs will often have very muscular front limbs and chest and thinner muscles over the back legs. This is because the dog uses the front legs to haul himself up and shifts all weight onto the front legs when walking. Watching muscle gain or loss is an easy and noninvasive way to monitor your pet, even during therapy.

Diagnosis of hip dysplasia is mainly via physical exam and X-rays. X-rays require special positioning and your dog may need to be sedated, especially if he or she is painful or scared. X-rays will determine the level of arthritis in the joint and the severity of malformation. Dogs typically cannot be diagnosed with hip dysplasia via X-ray until they are a minimum of two years of age, because the skeletons of larger dogs can continue to develop during the first two years of life.

Special note: the hip-screening procedure known as PennHIP (PennHIP stands for the University of Pennsylvania Hip Improvement Program) has proven to be the most accurate and precise method to measure hip laxity and subluxation. This screening method can identify dogs that are susceptible to developing hip dysplasia as early as 16 weeks of age. Early identification benefits breeders and allows veterinarians to advise pet owners on lifestyle modifications and treatments before the onset of pain or arthritis. Unfortunately, this test may not be available in your area as veterinarians must receive specialized training and quality-control exercises before becoming certified to perform the PennHIP procedure.

Alternative causes of lameness in the rear legs of dogs include torn cranial cruciate ligament rupture: up to 1/3 of dogs referred for treatment of hip dysplasia are suffering from concurrent cranial cruciate ligament rupture in the knee. Other possible causes include panosteitis, degenerative myelopathy, stifle arthritis, or lumbosacral disease.

Hip Displaysia: Surgeries, Medications, and Complementary Therapy

Treatment of hip dysplasia include medical or surgical treatments. Therapies are chosen based upon the patient’s age, size, level of activity, severity of disease or arthritis, and financial considerations of the pet owner.

Medical treatment for hip dysplasia is the same for old or young dogs no matter what stage of disease and consists of pain control, joint supplements, maintaining a healthy weight and muscle mass, and exercise therapy. Passive range of motion exercises can reduce joint stiffness and maintain muscle mass, and hydrotherapy in the form of swimming is an excellent non-impact form of physical therapy.

It’s important to note that without correction of joint instability, medical treatment is considered palliative in nature. Unless corrective surgery is performed early in the course of disease, arthritis in the form of degenerative joint disease usually gets worse over time. For a full list of medical therapies available, please visit treatment for arthritis (put a hyperlink to the definitive guide for arthritis treatment section).

Surgical therapy differs depending on multiple factors, such as the age and size of the dog. Goals of surgery vary based on the needs of the dog and can include:

In very young dogs (less than 20 weeks) who are exhibiting signs of hip dysplasia, a surgical option called a juvenile pubic symphysiodesis can improve the hip joint and decrease risk of arthritis.

In dogs 6-12 months of age without arthritis, your veterinarian may recommend a double or triple pelvic osteotomy (DPO or TPO). This surgery involves cutting the pelvis to correctly align the ball and socket joint of the hip to reduce pain and decrease arthritis later in life. This surgery can be successful, but success depends on the age of the dog, the degree of subluxation of the hip joint, the amount of arthritis already present, and the activity level of your dog. Your veterinarian will be able to tell you if this is a good surgical option for your dog.

In dogs that already have painful arthritis associated with hip dysplasia, a surgery called femoral head ostectomy (FHO) can help. In this procedure, the femoral head (the ball) is removed surgically, thus removing the connection between the leg and the pelvis and the source of pain. The joint stabilizes by scarring down over the course of several months. Dogs that undergo this procedure benefit greatly from physical therapy, as surgical success depends partially on the strength of the muscles surrounding the joint. FHO tends to be more successful in smaller dogs because they weigh less; however, this surgery can also benefit large dogs if they are kept at a healthy weight and are exercised to maintain strong muscles. Dogs who have this procedure performed usually have permanent, non-painful changes to their gait and some muscular atrophy.

Pet owners with very large dogs with severe disease can also elect to pursue a total hip replacement (THR). This is considered a “salvage procedure” in mature dogs with severe arthritis that is not adequately responsive to medical therapy. One joint is operated on at a time. In over 90% of cases, dogs that receive a total hip replacement become pain-free Eighty percent of dogs only need one hip replaced, though 50% of dog owners that elect to have a THR now choose to have both joints replaced, one after the other (source: Blackwell’s 5 Minute Vet Consult, sixth edition). There are limitations with the surgery, however. The implants have a limited life expectancy, and complications include luxation of the joint, implant infections, and nerve damage.

How to Exercise a Dog With Hip Dysplasia

What Is Elbow Dysplasia?

X-Ray of a Dog With Elbow Dysplasia

What Causes Elbow Displaysia?

Elbow dysplasia is a complicated disease that may comprise one to four developmental abnormalities that lead to malformation of the elbow. If untreated, these malformations can cause arthritis. The four abnormalities that can occur are incongruity of the joint, ununited anconeal process (UAP), osteochondritis dissecans (OCD), and fragmented coronoid process (FMCP).

Joint incongruity is caused by abnormal growth of the leg bones that lead to abnormal wear of cartilage in the elbow joint. In contrast to the hip joint, which is a ball and socket joint, the elbow joint is considered a hinge joint. A good comparison is to think of the elbow as a cabinet hinge: if the cabinet is hung poorly, the hinge will wear abnormally, and eventually the hinge will be damaged and the cabinet door will begin to sag and not close properly. The same thing happens in dysplastic elbows.

In UAP (ununited anconeal process), two parts of the ulna (a front leg bone that is involved in the elbow joint) that are supposed to fuse together by 5 months of age fail to do so. This results in a loose piece of bone that rattles around in the joint causing inflammation. This condition is thought to be caused by a combination of genetics and abnormal rate of growth, and German Shepherds seem to more affected than other breeds.

OCD (osteochondritis dissecans) is caused by abnormal development of cartilage on the surface of the humerus, resulting in a flap of cartilage that causes pain. OCD is thought to be a genetic disease and is usually seen in dogs from age 6 months to 2 years.

FMCP (fragmented coronoid process) is considered the most common cause of elbow dysplasia. In FMCP, a bone chip off the ulna causes inflammation and arthritis. The cause of FMCP is still unknown, but may be the result of abnormal mechanical stress on the elbow joint.

All of the causes of elbow dysplasia are considered to be at least partly due to genetics. Chances are if a dog has elbow dysplasia he or she will pass that on to offspring; dogs with elbow dysplasia should not be bred.

Elbow dysplasia is considered to be one of the most common causes of forelimb lameness and elbow pain in large breed dogs of all ages. Labrador Retrievers, German Shepherds, Rottweilers, Bernese Mountain Dogs, and Newfoundland dogs have a high incidence of elbow dysplasia. Risk factors for development of elbow dysplasia include rapid growth, high calorie diet, improper nutrition, and rapid weight gain. Dogs can often have disease in both elbows.

Other causes of elbow pain include panosteitis, trauma to the joint, cancer, or infectious arthritis.

Elbow Dysplasia: Signs and Symptoms

Dogs with elbow pain may exhibit the following signs:

Elbow Displaysia: What To Expect at the Veterinary Office

Your veterinarian will feel all your dog's bones, muscles, and joints.

During your visit, your veterinarian will take a history from you and do a full examination of your dog. This will usually include you walking and trotting your dog around so the veterinarian can assess your dog’s gait. Your veterinarian will then feel all the bones, muscles, and joints. They will test for pain. They will move joints through their range of motion while feeling the joint for any swelling or crepitus. Dogs affected with elbow dysplasia typically are painful when the elbow is extended.

Your vet will most likely check neurological reflexes as well. When there is thickening, arthritis or degenerative changes around a joint, your dog will show fairly predictable patterns with each joint.

Your veterinarian will feel for muscle mass on your dog while he or she is standing and compare muscles on each side. Arthritis anywhere in a leg will cause loss of muscle mass over the entire leg, not just around the affected joint. (Loss of muscle mass can also be secondary to spinal or nerve dysfunction; your veterinarian will determine whether the condition is musculoskeletal or neurological.)

Diagnosis of elbow dysplasia is typically done via radiography (X-rays). Depending on your dog’s level of pain, sedation may be required to get diagnostic X-rays. Other imaging that may be recommended include CT, MRI, or arthroscopy. Depending on the pet, the veterinarian may also recommend bloodwork or a joint tap.

Elbow Displaysia: Surgeries, Medications, and Complementary Therapy

With proper medical or surgical management, most dogs with joint dysplasias can lead normal lives.

Treatment for elbow dysplasia depends which of the four joint abnormalities are present. Treatment of elbow dysplasia includes medical or surgical treatments. Therapies are chosen based upon the patient’s age, size, level of activity, severity of disease or arthritis, and financial considerations of the pet owner.

Medical treatment for elbow dysplasia is similar for old or young dogs no matter the stage of disease, and consists of pain control, joint supplements, maintaining a healthy weight and muscle mass, and exercise therapy. Passive range of motion exercises can reduce joint stiffness and maintain muscle mass.

It’s important to note that without correction of joint instability, medical treatment is considered palliative. Unless corrective surgery is performed early in the course of disease, arthritis in the form of degenerative joint disease usually gets worse. For a full list of medical therapy available, please visit treatment for arthritis (put a hyperlink to the definitive guide for arthritis treatment section).

Surgical therapy differs depending on multiple factors, such as the age and size of the dog. Factors that worsen the prognosis include the severity of arthritis and the age of the dog; prognosis for a good outcome with surgery gets worse the older the dog. To illustrate the point, if your doctor recommends surgery to you for an abnormal joint, the sooner the joint is treated the higher likelihood the surgery will be successful.

The goal of surgery is to correct the joint instability and reduce the likelihood of developing arthritis.

For UAP (ununited anconeal process), there are four surgical options available: removal of the loose piece of bone, lag screw fixation, osteotomy of the proximal ulna, or lag screw fixation plus dynamic proximal osteotomy. The orthopedic surgeon will recommend a surgery based upon the amount of arthritis already present in the joint and the dog’s age.

For OCD (osteochondritis dissecans) and FMCP (fragmented coronoid process), surgery consists of removing loose bone fragments within the elbow joint.

Elbow joint incongruity is more difficult to correct surgically. Currently there are three options available: dynamic proximal ulnar osteotomy, intra-articular osteotomy, coronoidectomy. All three options are controversial, and an extensive conversation with your veterinarian will be needed to determine what is the right course of treatment for your dog.

Arthroscopic surgery is considered superior for elbow surgery. It allows good visualization of the joint and is minimally invasive.

Post-operative recovery of dogs undergoing elbow surgery is relatively short: a minimum of 4 weeks is recommended for healing, and active movement of the affected joint(s) is encouraged to promote healing. Your veterinarian will prescribe physical therapy exercises for you to perform at home.

What Is Osteochondritis Dissecans?

The joints most commonly affected are the shoulder joint, the elbow joint, the knee joint, and the ankle.

What Causes Osteochondritis Dissecans?

Osteochondritis Dissecans (OCD) is caused by abnormal development of cartilage within a joint. OCD is a genetic disorder that can be exacerbated by environmental causes, such as improper nutrition, for example diets that are inappropriately high in calcium for large breed puppies, or excessive exercise in a growing puppy. In OCD, the cartilage cells in a growing joint do not divide and differentiate normally, causing abnormally thickened areas of cartilage that interrupt the articular surface and cause abnormal rubbing within the joint. Normally, cartilage cells receive nutrition from the synovial fluid within the joint. In OCD, the thickened cartilage disrupts the metabolism of the joint, and the starving cells die, resulting in degenerated cartilage. Thickened cartilage can also crack and develop fissures or a flap of cartilage within the joint that can be painful, causing limping in the affected leg.

The joints most commonly affected by OCD in the dog are the shoulder joint, the elbow joint, the knee joint, and the ankle (hock). Less commonly affected joints include the hip, the knee cap, and the vertebral joints of the spine. The most common breeds that are afflicted with OCD include Newfoundlands, Bernese Mountain dogs, English Setters, Great Danes, Labrador Retrievers, and Rottweilers. All large and giant breed dogs are at risk. Growing dogs between 4-8 months of age are most at risk for development of signs of OCD, but signs of arthritis secondary to OCD can occur at any age.

Osteochondritis Dissecans: Signs and Symptoms

Osteochondritis Dissecans: What To Expect at the Veterinary Office

Your veterinarian will carry out a full examination of your dog.

During your visit, your veterinarian will take a history from you and do a full examination of your dog. This will usually include you walking and trotting your dog around so the veterinarian can assess your dog’s gait. Your veterinarian will then feel all the bones, muscles, and joints. They will test for pain. They will move joints through their range of motion while feeling the joint for any swelling or crepitus. Dogs affected with OCD typically are painful when the joint is extended, flexed, or rotated.

Your veterinarian will feel for muscle mass on your dog while he or she is standing and compare muscles on each side. Arthritis anywhere in a leg will cause loss of muscle mass over the entire leg, not just around the affected joint. (Loss of muscle mass can also be secondary to spinal or nerve dysfunction; your veterinarian will determine whether the condition is musculoskeletal or neurological.)

Diagnosis of OCD is typically done via radiography (X-rays). Depending on your dog’s level of pain, sedation may be required to get diagnostic X-rays. Other imaging that may be recommended include CT, MRI, or arthroscopy, which may be useful for certain types of OCD. A joint tap may also be indicated, depending on the pet.

Osteochondritis Dissecans: Surgeries, Medications, and Complementary Therapy

OCD in the shoulder and elbow is treated with surgical correction of the cartilage defect, and most patients do very well and have a good prognosis with surgery. Surgery for OCD in the stifle and hock (ankle) is controversial: most patients develop degenerative joint disease (arthritis) even with surgical treatment. Your veterinarian will recommend the best procedure for your dog.

Post-operatively, it is important to note that you will need to limit your dog’s activity for 4-6 weeks to allow healing.

It’s important to note that without correction of joint instability, medical treatment is considered palliative. Unless corrective surgery is performed early in the course of disease, arthritis in the form of degenerative joint disease usually gets worse. For a full list of medical therapy available, please visit treatment for arthritis (put a hyperlink to the definitive guide for arthritis treatment section).

References:

Textbook of Small Animal Surgery, Ed: Douglas Slatter, 3rd edition. Pub. Saunders of Elsevier Science, Philadelphia, 2003.

Handbook of Small Animal Orthopedics and Fracture Repair, Ed: D Piermattei, G. Flo, C. DeCamp, 4th edition. Pub. Saunders of Elsevier Science, Philadelphia, 2006.

Small Animal Surgery, Ed. T. Fossum, 3rd edition. Pub. Mosby of Elsevier Science, St. Louis, 2007.