What this means
The weakness often begins subtly. Your dog has more trouble getting up from lying down, is reluctant to jump or climb stairs, the back end sways when walking, and the nails start scraping on the ground. Sometimes you notice your dog knuckling over onto the top of a hind paw, or placing the feet in an odd way.
It helps to tell weakness from pain. A dog may be unwilling to use its legs because the joints or back hurt, but it may also be unable to, because signals from the spinal cord or the nerves are not getting through. Tell the vet whether the weakness came on suddenly or over months, whether both legs are weakening equally, whether your dog shows pain when touched, and whether it controls urinating and passing stools.
Many diseases of the spine and nerves develop slowly, and the first signs are easily put down to age or tiredness. So write down what you see: how your dog rises, how it walks, whether it slips on smooth floors, whether the legs tremble after a walk. Those notes, especially when compared over a few weeks, help a great deal in working out what is happening.
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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Degeneration of the spinal cord
A slowly progressing disease of the spinal cord, especially in older dogs, weakens the link between the brain and the hind legs. It does not cause pain, but your dog steadily finds it harder to control the back half of its body.
About the condition: Degenerative myelopathy -
Disease of the discs between the vertebrae
A bulging or ruptured disc presses on the spinal cord or the nerves. Weakness can appear suddenly or gradually, often with back pain or reluctance to move.
About the condition: Intervertebral disc disease -
Disease of the peripheral nerves
When the nerves that carry signals to the legs weaken, the muscles get weaker instructions and tire. At first this is easy to mistake for tiredness or old age.
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Disease of the motor cells of the spinal cord
An inherited disease in which the spinal cord cells that control the muscles die off. It shows in young dogs, and the weakness and muscle wasting grow.
About the condition: Spinal muscle atrophy -
Pain in the hips or knees
Sore joints can look like weak legs, because your dog avoids putting weight on them. Limping, stiffness on rising or reluctance to climb usually go with it.
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General weakness from illness
A serious illness or ageing weakens the whole body, and the hind legs often begin to buckle first. Your dog is also duller and eats less.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Whether your dog has more trouble rising or buckles on the hind legs
- Whether the legs slip on smooth floors, tremble or drag, with the nails scraping the ground
- Whether both legs are weakening equally or one more than the other
- Whether your dog shows pain when the back or joints are touched
- Whether your dog controls urinating and passing stools
- Whether the weakness came on suddenly or over weeks and months
When to book a routine visit
Book a visit if the hind legs are weakening, your dog has more trouble rising, buckles or slips, even without signs of pain. If the weakness came on suddenly or your dog can no longer stand, 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.
- Polyneuropathy Nerves and muscles Polyneuropathy is a disease in which many of the peripheral nerves, which carry signals between the spinal cord and the muscles, are damaged. When the nerves work less well the muscles weaken and coordination suffers, and in some cases the voice or swallowing is affected too. Polyneuropathy can be inherited or arise from other diseases, so its cause and course are for a vet to assess.
- 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.
- Degenerative myelopathy Nerves and muscles This is a slowly progressing disease of the spinal cord that, in older dogs, gradually weakens the connection between the brain and the hind legs. It is not painful, but over time the dog finds it harder and harder to control the back half of the body. The disease is linked to inherited factors, and whether a change in gait comes from it or from something else is for a vet to determine.
- Intervertebral disc disease Bones and joints Intervertebral disc disease is a condition in which the discs that cushion the spine between the vertebrae degenerate, bulge or rupture and start pressing on the spinal cord or nerves. This causes pain and, in more serious cases, weakness or even paralysis of the legs. The damage can happen suddenly, even after a perfectly ordinary jump, or build up gradually, so it is not something to wait out.
Body systems: Nerves and muscles Bones and joints