Muscle atrophy in Dogs

Muscle atrophy in dogs is sometimes  noticed with some parts of your dog’s body (such as the hips, hind legs, neck or face) becoming “thinner” or weaker than usual. This thinning is due to a loss of muscle mass known as muscle atrophy.
Also called muscle wasting, muscle atrophy is usually a sign of an underlying problem.

Muscle atrophy in dogs causes and treatment

There are three main causes of muscle atrophy:
• Aging
• Disease
• Disuse
In most cases, there is a combination of two or more causes.

How does Aging affect atrophy in dogs ?

As dogs get older, their bodies begin to develop problems such as reduced energy, loss of vision and/or hearing, susceptibility to infections and heart problems. Bone and joint diseases such as arthritis are also common. Any of these would lead to reduced activity, a tendency to sleep longer and loss of interest in playing. When the muscles used for exercise are not being put to use, they begin to waste away.
Aging dogs have reduced levels of growth hormone and are less able to process protein, which is needed to build muscle mass.
Different breeds of dogs age at different rates. Large-sized breeds such as Great Danes tend to age quicker, becoming “seniors” around age 7 (human years), as opposed to 10 years for tiny and toy breeds.
Muscle wasting that is due to aging is usually mild and shows on the hind legs and hips of senior dogs. Severe muscle atrophy or atrophy around the head and neck of your dog should prompt a visit to your veterinarian, no matter your dog’s age.

Which Diseases can cause muscle atrophy in dogs ?

There are many conditions that can cause muscle atrophy in dogs. These diseases usually have other accompanying symptoms. Inflammation of the muscle (myositis) is caused by an abnormal immune reaction of the body directed against the muscle, or response to a parasite or virus.
Myositis can affect only one muscle or a group of muscles (polymyositis). In the early stages, the muscles swell up, and then atrophy follows. If your dog is having difficulty opening its jaw in addition to losing muscle mass in the head or face, it may be suffering from masticatory muscle myositis, a disease of the muscles used for chewing.
Muscle atrophy accompanied by an unusual or unsteady gait, lameness, paralysis or urinary incontinence may be due to degenerative myelopathy, a disease of the spinal cord which is more common in German Shepherds. Hind limbs are affected first, then the front legs. The cause is not known, and there is no effective cure.
Atrophy in most of the cases is a natural consequence of aging and disease. As occurs in humans, when a group of muscles is not used, wasting occurs. Regular movement increases blood flow to a muscle, so inactivity means that less of the nutrients needed for growth would be delivered, leading to reduced muscle mass.

Treatment of Muscle atrophy in Dogs

In the absence of disease, muscle atrophy can be treated with regular exercise and proper feeding. Weight loss may also be recommended to ensure that the dog is at a healthy weight, thereby reducing the load on bones and joints.
High dose steroids are given initially to treat myositis by suppressing the body’s immune system. The dose can then be reduced after the disease has been controlled. However, there is the risk of suppressing the immune system too much, making your dog more prone to infections.
In the rare cases of myositis caused by an infection or cancer, treatment is aimed at the cause. Outcome in such cases is however not always favorable.

Will my dog get better when suffering from muscle atrophy?

How your dog fares depends on the cause of the muscle atrophy and how well it is treated. Dogs should be monitored closely during treatment to ensure that they are getting better and that the treatment is not doing more harm.
Regular checks are important for your dog’s health. If you have any concerns, please see your veterinarian.

Muscle Atrophy in Dogs – various cases

Muscle atrophy is the loss of muscle mass. It is also known as muscle wasting.
Muscle atrophy in dogs is usually a sign of an underlying problem.
The main functions of muscles are movement and maintenance of posture. Muscles are the only tissues in the body that can contract to move the body, so a loss of muscle mass would affect or reduce movement.
Paradoxically, a reduction of movement also leads to muscle atrophy, causing a vicious cycle of disuse of muscles leading to muscle wasting, which in turn reduces movement.
Apart from disuse, other causes of muscle atrophy are diseases and aging.

Dog muscle atrophy due to aging

Like in humans, aging dogs have reduced energy levels and are prone to bone and joint problems such as arthritis. Arthritis is inflammation of the joints. It causes pain when your dog moves the joint, so he would naturally be reluctant to carry out any exercise involving that joint. Unfortunately, when the muscle is not used, it wastes away.
Muscle atrophy that is due to aging is usually mild and is more easily seen on the hind legs.
Muscle atrophy may occur in one part of the body (such as the legs, hips or even on the head). It can also be generalized (all over the body).

Dog losing muscle all over body

If your dog is losing muscle mass all over the body, (and is being fed properly), he may be suffering from polymyositis, a condition in which groups of muscles is inflamed. This inflammation usually occurs when the body’s immune system attacks the muscles. It can also result from the presence of a parasite or virus. In the early stages of polymyositis, the muscles first swell, and there is pain and weakness. Muscle wasting then follows.
Steroids are used to treat polymyositis. The steroids suppress the body’s immune system. However, there is a risk of too much suppression, which can make your dog more susceptible to infections.

Dog losing muscle mass in one leg

Loss of muscle mass in one or more legs is usually due to a lack of exercise of the affected leg, and pain is the most common culprit. Pain can result from injury or arthritis. If your dog has had surgery on one leg, he can develop muscle atrophy while recovering because of inactivity.

Dog losing muscle mass in hips

Wasting of the hip or thigh muscles may be due to hip dysplasia. Hip dysplasia is a disease of the hip in which the ball-and-socket joint is malformed, so the thigh bone cannot fit properly into the hip bone. Large-sized breeds such as Great Danes, Saint Bernards and German Shepherds are more likely to have hip dysplasia. It usually begins when a dog is still young, but can occur in older dogs as a result of arthritis. Dogs with hip dysplasia may also have pain in the hips, difficulty getting up, difficulty running, jumping or climbing stairs and hip joint looseness.

hip_dysplasia muscle wasting

Bilateral hip dysplasia by Joelmills [ CC-BY-SA-3.0], via Wikimedia Commons


Anti-inflammatory drugs can be given to dogs with arthritis and hip dysplasia to control pain and inflammation. Your dog must also be at a healthy weight, to avoid putting undue load on the bones and joints. Your vet will also probably recommend physiotherapy to help to stretch ligaments and improve blood flow to the affected muscle, so as to hasten recovery.
Some supplements have also being proven to be helpful in the treatment of arthritis and hip dysplasia. They include N-acetyl Glucosamine and chondroitin. They help to regenerate the cartilage in the joints, thereby slowing down the progression of the disease.

Dog losing muscle mass in hips

A Labrador Retriever standing with hind legs close together to compensate for hip dysplasia

 

Dog hind leg problems and Canine degenerative myelopathy

degenerative_myelopathy_stance

Canine degenerative myelopathy  by Joelmills [ CC BY-SA 2.5-2.0-1.0], via Wikimedia Commons

Canine degenerative myelopathy may also be the cause of your dog losing muscle mass in the hips and hind legs. It is a disease in which the spinal cord degenerates. It is also thought to result from the action of the immune system. The hind legs are usually affected first, then the front legs. It is more common in German Shepherds. There is no effective cure or preventive measure.

Dog muscle atrophy in the head

 

Dog muscle atrophy in the head

A 2-yr-old pedigree American Pit Bull Terrier, previously in excellent condition, with masticatory muscle myositis. There was a sudden onset of ophthamalic symptoms–third eyelid protrusion–before the onset of noticable trismus. Within a 2-wk period, the eyes were bulging and trismus progressed to the point that jaws could be opened less than 1 cm, even under anaesthesia. Inflammation of jaws was more pronounced on the left side. Vision was permanently lost in the left eye.

If your dog is losing muscle mass in the head or face, there is cause for concern as he may have masticating muscle myositis, an immune-mediated reaction of the body against the muscles used for chewing. These muscles swell first, and then begin to atrophy. Your dog will also have difficulty in opening the jaw and bulging eyes and a sunken head.
A disease of the nerves supplying the muscle used for chewing, known as trigeminal neuropathy, can also cause your dog to lose muscle mass in the head. However, dogs with this condition cannot close the jaw, so the mouth hangs open.

Muscle atrophy in dogs

Masticatory Muscle myositis dog by Kalumet, by permission of the owners (Own work) [CC BY 2.5], via Wikimedia Commons


Muscle mass usually does not return fully after treatment of any condition without regular exercise and physiotherapy. Your dog needs to be monitored closely during and after treatment to ensure that they are getting better.
Aging dogs may not be able to do as much as they used to, but they must engage in regular exercise to keep their muscles healthy.
If you have any concerns about your dog’s health, please see a vet so that he can be diagnosed correctly..

 

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