What this means
Muscle wasting often begins unnoticed. Your dog's body can look the same, only the legs are thinner, the thighs less rounded, the spine and hip bones stand out more and the head shows hollows at the temples. Look at your dog from above and from behind: are both sides symmetrical, or does one leg look thinner than the other?
It matters to tell muscle wasting from general thinness. A thin dog has less fat and the whole body looks smaller, while with wasting muscles the bones stand out and the shape of the body changes, even if the weight is similar. Weakness often goes with wasting: your dog tires sooner, climbs stairs with more difficulty, slips or drags its feet.
Muscles waste when they no longer receive signals from the nerves, when the muscle itself is diseased, or when a leg goes unused for a long time because of pain. That makes it more important to notice since when it has been happening, whether it began in one leg or the whole body, and whether the skin, the voice or swallowing are changing too. Only a vet who examines your dog can find the exact cause.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
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Disease of the peripheral nerves
When the nerves that carry signals to the leg muscles weaken, the muscles receive fewer and fewer instructions and waste. At first this is easy to mistake for tiredness or old age.
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Inherited muscle disease
Some muscle diseases are inherited and slowly weaken the muscle fibres. Your dog tires sooner, walks with more difficulty and sometimes swallows with more difficulty.
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Disease of the motor cells of the spinal cord
When the cells in the spinal cord that instruct the muscles die off, the muscles weaken and waste. This is usually seen in young dogs.
About the condition: Spinal muscle atrophy -
Inflammation of the muscles
Some inflammatory diseases affect both the skin and the muscles. Your dog may have skin changes on the face or paws, and the muscles around the head may waste and make eating harder.
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Muscles unused because of pain
If your dog protects a painful leg for a long time, the unused muscles shrink. That leg then looks thinner, and your dog limps or avoids putting weight on it.
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General illness or ageing
A serious long-term illness or ageing can reduce muscle mass across the whole body. Your dog looks thin and weaker, and the bones show more.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Where on the body the muscle has shrunk, and whether both sides match
- Whether your dog tires sooner or climbs stairs with more difficulty
- Whether the legs slip, drag or tremble
- Whether the skin has changed too, especially on the face, ears or paws
- Whether your dog swallows with more difficulty, chokes more or the voice has changed
- Since when this has been happening and whether it is speeding up
When to book a routine visit
Book a visit if you notice the muscles shrinking, one leg thinner than the other, or your dog tiring sooner or moving with more difficulty. If swallowing, breathing or standing is difficult as well, go straight away.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Adult-onset neuropathy Nerves and muscles This is an inherited disease of the peripheral nerves that appears once a dog is already an adult: the nerves carrying signals from the spinal cord to the leg muscles gradually weaken. As a result the muscles receive ever weaker signals, waste away, and the dog finds it harder to control its legs. The disease progresses slowly, so the first changes are easy to mistake for tiredness or old age.
- Degenerative myopathy Nerves and muscles Degenerative myopathy is an inherited muscle disease in which muscle fibres gradually waste away and weaken. Because it affects more than one group of muscles, a dog may in time find it harder to walk, keep up with exercise and sometimes even to swallow. It progresses slowly, and whether weakness comes from it is for a vet to determine.
- Spinal muscle atrophy Nerves and muscles Spinal muscle atrophy is an inherited disease in which the motor neurons in the spinal cord, which tell the muscles to move, gradually die off. Without those signals the muscles weaken and waste away. The disease appears in young dogs and progresses over time, so its first signs are worth showing to a vet.
- Dermatomyositis Skin and coat Dermatomyositis is an inherited inflammatory disease that affects the skin and sometimes the muscles. Its signs can appear at a young age, and it can range from barely noticeable skin changes to muscle wasting that makes eating and swallowing difficult. Damaged skin can leave lasting scars and bald patches.
- Centronuclear myopathy Nerves and muscles Centronuclear myopathy is an inherited muscle disease in which the muscle fibres do not develop properly, leaving the puppy short of strength and stamina. It becomes apparent in the first months of life and affects muscles throughout the body. A genetic test exists, so breeders can check whether their breeding dogs carry it.
Body systems: Nerves and muscles Skin and coat