Muscle Atrophy in Dogs: 10 Surprising Causes

One of the things you or your veterinarian may notice as your dog gets older is muscle atrophy. Muscle atrophy in dogs may seem minor, but it’s a bigger problem than you might think.

Muscles are a crucial part of the body, and your dog losing muscle mass can harm them in many ways. Muscles’ primary function is to work with the skeleton to move the body. So if your pup is losing muscle, they may not be able to do things they used to love, like go for hikes or chase a ball. 

Muscles also help protect the bones and joints. So, muscle atrophy in dogs can mean joint issues, like arthritis, can be more painful. This can increase the risk of injury when doing everyday activities like jumping on and off furniture or walking around on hard floors.

Let’s talk about why muscle atrophy is such a big deal!

Dog Muscle Anatomy: A Brief Overview

Dogs, like humans, have muscles all over their bodies. There are very few places where their bones are not covered with at least one layer of muscle. And many areas have three or more layers. All these muscles are used daily to hold their bones together. Even teeny tiny muscles like those in the hips or jaws serve a purpose.

While there are a lot of muscles in a dog’s body, there are a few groups we want to focus on.

• Head and neck: help with chewing, playing, movement of the ears and head, and even facial expressions. 
• Shoulder: help with walking, running, climbing, playing, and jumping. 
• Hip and thighs: help with walking, running, and jumping. 
• Spine: helps with everything the front and back legs do, as well as the ability to do things like shake themselves off or roll on the ground.

Technically, these muscles are all connected and work together. So, anything that changes with one set of muscles automatically affects the rest of the body as well.

What is Muscle Atrophy in Dogs?

The fact that all muscles are needed means that all muscle atrophy is important, but some areas are more common or noticeable than others. Muscle atrophy in dogs is also commonly called muscle wasting or muscle loss. You may hear people talk about muscle weakness, and while muscle atrophy does cause weakness, you can see muscle weakness without atrophy. 

So, what is muscle atrophy? 

Muscle atrophy is when the muscles shrink from their original, healthy size and shape. The size and shape of muscles depend on how much they are used and whether the nervous system is functioning normally. Because of this, there are two types of atrophy: disuse atrophy and neurogenic atrophy.

Disuse atrophy

Occurs when muscles shrink because they are not being used much. This is commonly seen in dogs after long periods of rest, typically while recovering from surgery, illness, or due to arthritis.

Neurogenic atrophy

This is when the muscles shrink because they are no longer communicating with the nervous system. The nerves that connect to the muscles send signals almost constantly, telling the muscles that they need to be ready to work. If those signals aren’t coming through, the muscles will start wasting away from the lack of stimulation.

The most common places for muscle atrophy in dogs are on top of the head and in the back legs, though it can also be seen in the front legs and on top of the back. When a dog’s muscles decrease, their day-to-day life becomes more difficult. Your furry friend may have trouble eating, chewing on toys, climbing stairs, playing, or even getting up off the floor. Their overlapping muscles work together to do these daily tasks, as well as hold organs in place and the skeleton together. We don’t think about muscles much, but they are SUPER important for our pet’s lives!

Is Muscle Atrophy in Dogs Painful?

Muscle atrophy is not usually painful. However, pain can be associated with diseases that cause muscle atrophy. Sometimes, like with arthritis, the disease is painful, and the muscle loss can make the pain worse. Other times, like with tetanus, the muscles themselves are painful due to the disease process taking place. And if something, like infection, is destroying muscle, that will certainly cause pain. If you are afraid your pup is painful due to muscle atrophy, talk to your veterinarian right away.

Signs and Symptoms of Muscle Loss in Dogs

Muscle wasting in dogs can show up in many different ways. What you notice in one dog may be less visible in another dog. 

For instance, you probably won’t see the muscle loss in a pup with a fluffy coat, but it’s pretty easy to see in a short-haired dog. If you live in a home with hard flooring, like wood or laminate, you’re more likely to notice your pup having difficulty getting up than if you have carpet. 

Difficulty with stairs will only be noticeable if you have stairs. Sometimes, changes can be subtle, like your dog no longer hanging out in the kitchen but sticking to the carpet in the sitting room. Pay attention to those early signs to get your pet help as soon as possible!

Some common signs of muscle wasting are:

• Avoiding certain types of flooring, like hardwood or laminate
• Bones sticking out on the head, shoulders, back, or hips
• Decreased ability to jump or climb
• Difficulty getting up from sitting or lying down
• Dragging toes
• Dropping food
• Falling with legs out to both sides (instead of both legs on one side)
• Having trouble on stairs
• Laying around more
• Legs looking skinny
• Looking wobbly or swaying from side to side while standing still
• Needing to go on shorter or easier walks
• No longer chewing on toys, bones, or sticks
• Not wanting to go on walks
• Refusing to eat hard food or treats
• Shaking legs when getting up, standing, or after exercise
• Slipping or even falling on slick surfaces like hardwood floors
• Weight loss (particularly in the back end)
• Wounds on elbows, wrists, hips, and ankles

Surprising Causes of Muscle Atrophy in Dogs

There are many, many causes of muscle atrophy in dogs. Below are some common causes you should consider if your pup struggles with this problem.

1. Arthritis and Joint Disease

Arthritis is the most common cause of muscle atrophy in dogs and is most common in older pets. Joint difficulties, injury or badly formed bones and cartilage, make it painful for your furry friend to move around. When your pup doesn’t move much, the muscles begin to atrophy from lack of use. Unfortunately, as the muscles atrophy, they provide less and less support to the joints. This lack of support means moving is more painful, so your pup will lay around even more. It’s not a fun cycle.

2. Improper Exercise (Too Much or Too Little)

As mentioned above, too little exercise causes muscle loss simply because the muscles aren’t being used. But did you know that too much exercise can also cause muscle atrophy in dogs? When the muscles are worked too hard, too long, or too frequently, the lack of rest leads to increased stress hormones. These hormones, particularly one called cortisol, can cause the muscle to break down and atrophy. Read more about cortisol in the next section!

3. Hormonal Imbalances

Another common cause of muscle atrophy in dogs is hormone imbalance. Hormonal imbalances can cause muscle wasting in several different ways.

Hyperthyroidism, or an overactive thyroid, is rare in dogs but causes muscle wasting as one of its many symptoms. The thyroid is one of the body’s control centers, so an overactive thyroid will increase your pup’s metabolism. An increased metabolism means your pup will need more calories to get through the day. If their food does not provide these calories, their body will find them. This can be done by breaking down fat and muscle tissue, ensuring other organs like the heart and the brain keep working.

Strangely, an underactive thyroid, or hypothyroidism, can also cause muscle loss and weakness. Hypothyroidism is much more common in dogs than an overactive thyroid. When the thyroid is underactive, your pup’s metabolism slows down. And tissues that require frequent repair or maintenance, like muscles, start to deteriorate. Over time, this results in your dog losing muscle mass.

A much more common cause of muscle loss due to hormones in dogs is hyperadrenocorticism (HAC). HAC is an abnormality of the adrenal glands (tiny glands on top of the kidneys) that causes them to produce too much cortisol. Cortisol is a hormone the body produces to help it respond to stress, and it is normal for your pup to have a little bit in their system at any given time. But when there is too much cortisol around, it tells the body to start storing more energy in the form of fat. This need to store fat means your pup will always feel hungry. And, when they can’t get enough energy from what they’re eating, they break down muscles to convert them to fat.

4. Overuse of Corticosteroids

Corticosteroids, commonly called steroids, are medications frequently used to treat a wide variety of diseases in dogs. These diseases range from allergies to diseases where the body is attacking itself to cancer and everything in between. Unfortunately, steroids can have many side effects. One of the most common long-term side effects of steroids is muscle wasting. Muscle wasting occurs because steroids mimic cortisol in the body, causing many of the same effects over time.

5. Chronic Stress and Anxiety

Stress and anxiety are bad for your pup in many ways, with muscle atrophy being only one of the problems they can cause. Chronic or long-lasting stress and anxiety cause an increase in cortisol. Just like with HAC and using steroids as medication, this can cause the breakdown of muscle over time.

6. Hidden Infections

Infections with bacteria, viruses, or fungal agents can have many effects. If an infection attacks the muscles or nerves, it certainly can cause muscle loss. However, even infections in other places on the body, such as the skin or internal organs, can eventually cause muscle wasting. Muscle loss could be due to the body’s increased needs while fighting the infection, or it could be due to increased stress hormones. Either way, if your pup is fighting an infection, especially a hidden one, you may see your dog losing muscle mass.

7. Other Diseases

While infections can sometimes cause muscle wasting, many other diseases have muscle atrophy as one of the main symptoms. These include heart disease, diabetes, cancer, protein-losing enteropathy or nephropathy, and various neurological diseases.

In some cases, like heart disease, we don’t understand why muscle wasting occurs. In some, like diabetes and cancer, the body’s nutritional needs have increased, and the muscle is broken down to provide those resources. There are even diseases where your dog’s body could start attacking the muscles and cause atrophy. In others, like protein-losing diseases, the cause is similar to when a dog isn’t eating enough protein in the first place. More about that next! 

8. Inadequate Nutrition

Feeding a low-protein diet can cause muscle loss in dogs. Muscle wasting due to malnutrition is most common in dogs eating vegetarian diets because getting enough plant protein can be difficult. It can also be seen with home-cooked and poorly formulated diets. Muscle loss due to poor nutrition starts with the normal process of muscles breaking down and repairing themselves. If there is not enough protein available to make the repairs, the body cannot replace the broken-down cells, and the muscle will shrink. On the other hand, some diseases are managed with low-protein diets. If you are trying to figure out the best food for your dog, ask your veterinarian for advice!

9. Genetic Disorders

Sometimes, a dog will be born with genes that cause muscle atrophy. Genetic disorders that can cause muscle loss include muscular dystrophy, myasthenia gravis, and several different myopathies. “Myopathy” just means “disease of the muscle,” but many of these genetic mutations are not well understood and don’t have a better description at this time. Some of these genetic problems are treatable, and some are not, so talk to your veterinarian if you are concerned about your pup having one of these conditions.

10. Environmental Toxins

Muscle atrophy due to toxins is less common now than it used to be but is still seen occasionally. There are two toxins produced by the bacteria Clostridium that can cause muscle wasting as part of their disease process. These processes are commonly known as botulism and tetanus and can be deadly without treatment. Botulism is most commonly associated with eating food that has gone bad and tetanus with infected wounds. Both cause muscle paralysis but in different ways. With botulism, the paralysis results in limp muscles, while with tetanus, the muscles clench until they become hard and don’t work anymore. Both can result in disuse atrophy if the primary disease isn’t treated quickly.

Another toxin that can cause muscle atrophy is becoming more common in the US. One type of rat poison, called bromethalin, can cause tremors, seizures, and brain swelling that may result in either disuse or neurogenic muscle atrophy. Bromethalin can cause problems that last for months, so muscle wasting can be slow as the disease progresses.

Diagnosing Muscle Atrophy in Dogs

A thorough physical examination is the first step. Your veterinarian will feel your dog’s muscles, particularly their legs and spine, looking for signs of muscle loss.

They will likely check the major joints involved in arthritis: the hips, knees, and elbows. They may also recommend X-rays for your pup to check for changes to its bones.

Next, your veterinarian may recommend different tests if they think the muscle atrophy is not due to arthritis. These can range from blood tests for genetic or autoimmune diseases to biopsies of the muscles or nerves looking for other diseases. Blood tests often need to be sent to specialized labs, so you may have to wait a week or two for results.

Biopsies require anesthesia so your veterinarian can collect a sample of the muscle or nerve. The clinic will then send the sample to a lab for analysis, so it often takes a week or more to get those results back. Which tests are recommended will depend on your pup’s age, breed, and history, and so will be customized by your veterinarian for your pet.

Management and How to Help Dogs Build Muscle

Once your pup has muscle atrophy, rebuilding it can significantly improve their quality of life. With more muscle, they will be better able to enjoy activities like going for walks, chasing balls, and maybe even getting up on furniture again! But remember, rebuilding muscle is hard work. Depending on why the muscle loss occurred in the first place, the approach may be different from one dog to another. Always check with your veterinarian for instructions specific to your pup.

Dogs with muscle atrophy are more likely to injure themselves in their day-to-day life. Muscle loss and weakness mean they can’t control their bodies as well as they used to, so they will tend to do things like slip and fall. Because of this, the first thing to do when your dog has muscle atrophy is to make sure you are keeping them safe.

There are many options for this. You could try products for your dog’s feet or toes to help them grip the ground. Or simply put something with a good grip, like yoga mats, all over your house. Using baby gates to block staircases can help keep your pup from falling down the stairs. Providing ramps instead of stairs can also help prevent tripping and falling. Lastly, using stairs to help your dog get on and off of furniture can help prevent injuries from unsafe jumps.

How to Help Dogs Rebuild Muscle

Protein

When you are trying to help build or rebuild muscle, the first thing to make sure of is that you are feeding enough protein. As mentioned earlier, too little protein can lead to muscle loss, so you must feed extra when building muscle. We usually aim for at least 18% protein when discussing dog food. If your pup is a working or hunting dog or has a particularly active lifestyle, they may need food with closer to 30% protein to meet their needs. Just remember that some diseases are managed with low-protein diets as well. So, always discuss your pup’s protein needs with your veterinarian before changing their diet.

Exercise

Beyond nutritional support, your pup will need a customized exercise plan to rebuild the muscle. Like a person would go to a physical therapist to help recover from an injury or illness, your pup should do the same. A veterinary physical therapist can create a plan just for your dog with exercises and instructions to help them safely rebuild the muscles they need. We don’t want to overdo it or try something too hard too soon and cause a new injury!

Muscle Atrophy Prevention Tips

There are several things you can do to prevent muscle atrophy in your pup. Of course, not every single type of muscle atrophy is preventable, but some simple things can help avoid the most common types of muscle loss.

Diet

First, make sure your dog is eating a diet that provides enough protein for their lifestyle. Most dogs will do well with the protein levels in most dog foods, but there are exceptions to every rule. If you think your dog needs more or less protein than “regular” food provides, ask your veterinarian for advice.

Exercise

Second, make sure your furry friend gets enough exercise. As we discussed earlier, too little exercise is one of the most common causes of muscle loss in dogs. Going for walks, chasing a ball, and even running around the house all count as exercise, but we need to make sure our pups are getting enough every day. That said, if your dog lays on the couch most of the week, it might not be a good idea to dive right into a big run on the weekend. Like with us, our pups need to work up to heavy exercise like that.

Know the Signs

Look out for those early signs and get help for your pup as soon as possible. Rebuilding muscle once it is gone is challenging, so prevention and early intervention are critical.

Breed

Some breeds, like Labradors and German Shepherds, are more susceptible to joint issues. Discuss joint health with your dog’s veterinarian early and often so you can get recommendations for their age, breed, and lifestyle.

Final Thoughts on Muscle Atrophy in Dogs

Muscle atrophy in dogs is a widespread problem and significantly decreases their quality of life. Being unable to run around and too weak to do what they enjoy is no fun! Unfortunately, not all muscle atrophy is avoidable. But, you can take some simple steps to keep your dog as comfortable as possible throughout their life. If you notice signs of muscle atrophy, talk to your pup’s veterinarian to figure out the best plan for them.

In addition, make sure to keep up with your pup’s regular check-ups. Veterinarians are very familiar with this problem and may notice some of those early changes even before you see them at home. Taking your dog to see the veterinarian when they are feeling well is essential for catching these things and will allow you to work together to put together the best plan for your pup!