Hypertrophic Osteodystrophy from Dr. Rachel Mar

Dr. Rachel Mar (@thevitalityvet) is an amazing resource for our large and giant breed dogs! This week she is discussing Hypertrophic Osteodystrophy, a common joint issue with rapidly growing, large breed dogs!

What is Hypertrophic Osteodystrophy?

Hypertrophic Osteodystrophy (HOD) typically affects both legs symmetrically which gives it the characteristic of 'growing pains'. HOD comes on rapidly and the affected dog will stop eating, become lethargic and stand or lay with their head pointed towards their belly. HOD is an orthopedic emergency because if not treated, it can affect the blood supply to the femur (thigh bone) leading to femoral head necrosis. HOD often requires the removal of the femur head in order to provide space for new bone growth.

Hypertrophic Osteodystrophy- Ortho Vet

What Happens When A Puppy Gets HOD?

When a young, rapidly growing puppy has Hypertrophic Osteodystrophy (HOD), there is rapid bone growth causing the long leg bones to spread apart and compress blood vessels and nerves. This causes pain and lameness in the affected limb. Symptoms of HOD can vary from case to case.

There are two types of HOD. There is the acute form, or the rapidly progressing one, and there is the chronic form. Both types are painful for puppies to experience, but each has a different rate of progression.

You may begin to first notice limping in the affected limb, but after a short time, it is often both limbs which are affected. When you feel the bones of the leg and foot, bones may be hot and swollen. Your puppy may be acting lethargic and not eating well. Additionally, most puppies with early onset of HOD are reluctant to move freely, stand up, or walk with normal gait. Maybe your puppy is shifting their weight from one leg to another. Additionally, puppies may lack appetite due to the increased inflammation and pain in their joints.

Sometimes, HOD can be accompanied by 'knuckling' of the joints, which is caused by the widening of bones in the joints. This knuckling can worsen to the point that your puppy cannot keep his weight on his toes while walking, and must walk with his leg straight or bear weight on his elbows.

This physical bowing out of the joints will look similar to a bow-legged appearance in humans. In a severe case of HOD that might cause knuckling joints, you may be able to feel warm/swollen joints and your puppy may develop a fever, so it’s important to have your puppy’s temperature checked if HOD is suspected.

'knuckling' of the joints dog
Image Courtesy of Great Dane Lady

In advanced stages of Hypertrophic Osteodystrophy, blood vessels and nerves can become so compressed that the affected limb may begin to die off since blood supply from the heart is cut off due to the compression caused by swollen bones in the leg. However, this only happens when the very early stages of Hypertrophic Osteodystrophy have been ignored for many months or more.

Diagnosis

If you suspect that your puppy has HOD, diagnosis can be made by radiographs (X-rays) and ultrasound. HOD is preventable with an appropriate puppy large breed diet or the addition of supplements if needed, such as Vitamin C and Vitamin E which can often reduce the risk of development. HOD often requires extensive orthopedic surgery to correct the damage done, however just because your puppy has received a diagnosis does not mean that surgery will be required.

Your veterinarian will want to take x-rays and run blood tests to determine if Hypertrophic Osteodystrophy is the cause of your dog's symptoms. You may be asked about your puppy’s diet and of course, your vet will conduct a physical exam to determine the degree of pain and lameness in each limb.

Image Courtesy of Andrea Matthews, DVM, Dip ACVR Assistant Professor of Radiology

Once Hypertrophic Osteodystrophy is confirmed by your veterinarian, it is important to seek further veterinary care immediately based on what is recommended for the next steps. HOD can be painful and cause distress for your puppy, and requires treatment immediately to prevent further issues.

What Causes HOD?

The primary causes of HOD in puppies remains unknown, however several factors are believed to be involved in Hypertrophic Osteodystrophy. The most common factors are rapid, unseasonable growth spurts that have become somewhat hereditary.

It has been suggested that the underlying cause of HOD is bone fragility secondary to altered calcium and phosphorus metabolism, resulting in increased resorption of bone matrix by immature osteoclasts (cells involved in bone remodeling). When large breed puppies are growing, the metaphyseal areas of their long bones are particularly susceptible to increased resorption by immature osteoclasts, resulting in a lack of bone cortex.

In puppies with HOD, the resultant thinning or complete loss of cortical bone exposes the usually avascular (aka bloodless) medullary cavity, which causes an acute increase in pressure. After the cortical bone is re-generated with new, more calcified bone by osteoblasts (cells involved in forming and maintaining bones), the pressure resolves.

Image Courtesy of Research Gate

Many medical conditions such as Panosteitis have been suggested to cause HOD or have symptoms that are very similar to HOD.

Other medical conditions such as Panosteitis have been suggested to be associated with HOD or have symptoms that are very similar to HOD.

Additional Suspected Causes of HOD Are:

Metabolic/Nutritional: With a lack of vitamin C, puppies can get HOD. Similarly, puppies with low blood calcium levels (hypocalcemia) are also at risk for this disease. It is recommended by some veterinarians to support your growing large breed puppy with Esther Buffered Vitamin C as a preventative measure in this disease. Too much or too little calcium and phosphorus in your puppy's diet may cause HOD. This is known as overnutrition/oversupplementation or a lack of nutrition.
Toxicity: Large puppies may develop the bone abnormality due to exposure to some kind of toxin. Some poisons of interest include lead or arsenic that puppies may be exposed to through their food or environment.
Infection: A bacteria or virus can also affect puppies, causing them to develop HOD. Other puppies may develop HOD secondary to a disease or problem in another body system, such as a bacterial infection, internal parasites, a fever caused by an infection or autoimmune diseases, or trauma such as with wounds
Breed Type / Genetics: In general, puppies who are large breed puppies (such as Great Danes), or puppies that have a parent with large bones, are more likely to develop HOD. Inherited hip dysplasia in the puppies' parents may increase their chance of developing HOD.
Undetermined: Many cases of HOD remain undetermined/unknown. Though many studies have been done, the causes of HOD are still in the air in some of the cases of the disease.

Treatment of HOD

The treatment for puppies diagnosed with Hypertrophic Osteodystrophy focuses on reducing the pain and swelling from swollen joints, as well as providing an appropriate diet to promote recovery.

In puppies whose disease is diagnosed early, good results have been obtained by combining a corticosteroid with a non-steroidal anti-inflammatory drug (NSAID). The use of one or the other alone has not been as effective. To date, no one single treatment has been found to be consistently effective for all puppies with HOD, but most puppies do well when treated early in the disease process.

In puppies without symptoms of HOD, there is no need for treatment. However, puppies with severe pain or lameness should be examined by a veterinarian immediately. Treatment often consists of pain medications, corticosteroids, and application of warm compresses to the joints.

When puppies are not treated for HOD, it is possible that they could develop crippling deformities in their legs or other parts of their body if the condition is left untreated.

In puppies that have been treated for HOD, it is important to administer a complete course of treatment. If puppies are showing signs of lameness after the treatment has been completed, a recheck should be performed by a veterinarian before puppies resume normal activity.

Activity for Puppies with HOD

Is it okay for your puppy to play and exercise when experiencing HOD?

Yes, puppies can exercise when experiencing HOD. Moderate exercise is actually encouraged when puppies are experiencing the disease, in order to assist in providing relief for their pain. However, the form of exercise is going to be dependent on your puppies pain levels and also going to be driven by protecting their joints.

When diagnosed with HOD as a puppy, some healthy forms of exercise may include:

Swimming: Swimming is a great, low impact form of exercise for puppies to participate in, especially puppies with HOD. This type of exercise will keep their muscles developed, but also allow them to support their joints through the buoyancy of the water. The weight of puppies at play can be very hard on their bones and joints, so this form of exercise is encouraged.
Leash walks: Not only do leash walks help puppies learn their manners, leash walks are also a great way to get puppies to exercise without overworking their joints or bones which can lead to HOD flare-ups. Leash walks can be short, but puppies need the mental stimulation of learning and obeying commands for this type of exercise to be effective. Make sure to always use protection against the hot pavement when walking your dog on leash, to avoid paw burns.
Mental Enrichment: This is not something you can force, but puppies need mental stimulation in order to be happy and healthy. Mental enrichment can be as simple as hiding a treat for puppies to find or playing catch with a favorite toy.
Stretching: Remember puppies are only puppies for a short time, so take the opportunity to stretch their bodies. Puppies can get stiff muscles and joints if they aren't stretched regularly, so never forget your puppy's flexibility exercises!

What type of exercise is NOT recommended when puppies have HOD? While puppies with HOD should be able to engage in light to moderate exercises when experiencing the disease, puppies should not participate in strenuous exercise. Such forms of exercise include:

Running: Never allow puppies with HOD to run long distances, especially while being forced (example: running on a leash next to a skateboard), until they are more fully developed. This activity puts puppies at risk for injuring their bones and joints because there is too much weight on their young bodies while they are working hard to grow. Your puppy is free to play in an open area, at their own pace, but never put them in situations where they are 'forced' to keep going when they might need a break.
Jumping: When puppies jump, it puts a lot of force on their bones and joints. Puppies with HOD should not participate in jumping until they are past their developmental stages; and even then puppies should be encouraged to do exercises that keep their joints safe such as swimming.
Strenuous play: Remember puppies experience fatigue just like adults, so puppies with HOD should not be forced to participate in strenuous play until they are past puppyhood.
Long walks: Long walks are often the source of pain that puppies experience when they have HOD. These puppies are pushed too hard for their body's comfort level and it can exacerbate their symptoms which could lead to bone damage.
Hard surfaces: Walking or playing continually on hard surfaces such as concrete can lead to more impact on puppy’s joints. Instead, take a walk in some grass or let your puppy play in sand or mud. The differing textures of surfaces will help them strengthen their muscles without the added pressure.

Image Courtesy of AKC

Make sure to check with your veterinarian to see which forms of exercises they encourage for your individual puppies needs.

Home Adaptations for Puppies with HOD

If your puppy gets diagnosed with Hypertrophic Osteodystrophy, there are ways you can adapt your home to create a more suitable living space for your pup’s joints.

Firstly, a home must be easy to navigate for puppies with joint disease. Their pain might limit them from doing things around the house that typical puppies can do.

Flooring: An easy way to make your home easier for puppies with HOD is by putting runners down in the hallways, rooms, and stairs. On slippery floors, the puppies could slip on them which will not harm their joints due to the slow motor function of puppies with bone disease. If you have hardwood flooring, you can put rugs with non-slip pads under them.
Stairs: If your puppies are slowly hobbling up the stairs, they could slip and fall back down. To prevent this, you can install carpet or runners on the staircase. You can also lift puppies slowly up the stairs by placing your hands around their belly or under their armpits. If your puppies are struggling with stairs, you can make an easy path of 3-5 steps to help them get up and down.
Furniture: Another way that you can make the home more suitable for puppies with HOD is by making furniture easier to climb onto. Keeping them off of the furniture and working to make sure they are not jumping on and off of couches and beds is an additional way of protecting their joints.
Ramps: If puppies with HOD begin to lose the ability to walk, it might be beneficial for you to install a ramp in your home in harder-to-access areas. This would make it possible for puppies who are essentially crawling up stairs with their front legs to go up and down stairs without too much effort. A ramp can also be beneficial for getting in and out of the car without unnecessary pressure.
Supportive Bed: Puppies with HOD have inflammation in their legs and hips which can cause pain when lying down or sitting in a certain position for too long. When puppies are experiencing this joint pain, it would be best to invest in a supportive, orthopedic bed. This type of dog bed will allow puppies to adjust themselves into comfortable positions while they are resting as well as keep them off of hard surfaces that can inflame their pain.

Conclusion

Although Hypertrophic Osteodystrophy can be a scary diagnosis, it is treatable and can be prevented with certain management. With treatment quick into diagnosis, puppies with HOD generally make a full recovery. There is a chance of relapse, but the puppies that do suffer from relapse can undergo treatment again and recover quickly.

Your puppy can still live a full life and gain a full recovery with the proper treatments. Being proactive and working with your veterinarian will ensure a full life for your puppy.