What this means
Sudden weakness in the hind legs is one of those changes that cannot be put off. A cat may suddenly be unable to stand or walk, drag the back of its body, cry out or yowl in pain, and the paws of its legs may feel cold, pale or an unusual colour. It often breathes fast or hard at the same time, sometimes with the mouth open.
One possible cause is a blood clot blocking the vessel that carries blood to the hind legs. It can happen to a cat whose heart is diseased, and sometimes it is the first sign that the heart is not healthy, even though the cat looked completely well before. Sudden weakness can also come from damage to the spine or nerves, an injury or other serious conditions, but they can only be told apart by an examination.
Do not wait for it to pass and do not try anything at home: the sooner your cat reaches a veterinary clinic, the better. Phone the clinic on the way and say that your cat's hind legs have suddenly weakened. If your cat has a heart diagnosis, say that too. Carry your cat carefully so as not to cause more pain.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your cat.
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A blood clot in a leg artery
A clot can block the vessel that supplies blood to the hind legs. They become weak or paralysed, cold and very painful.
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Heart disease
Some heart disease encourages clots to form. Sometimes sudden leg weakness is the first sign that a cat's heart is diseased.
About the condition: Heart disease -
Damage to the spine or nerves
Problems with the spinal cord or nerves can suddenly take away control of the hind legs, although the legs are not usually cold.
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Injury
A fall, a blow or another injury can damage the spine, pelvis or legs and cause sudden weakness or limping.
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Severe general weakness
Some illnesses can weaken the muscles so much that a cat can no longer stand or walk, and the legs seem to buckle.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Exactly when the legs weakened and whether anything happened before
- Whether the legs are cold, pale or an unusual colour
- Whether your cat cries out or complains when you touch it
- How it breathes: fast, hard or with the mouth open
- Whether it is passing urine and stools or the litter box stays dry
- Whether your cat has previously been diagnosed with heart disease or a heart murmur
When to book a routine visit
This is an emergency, and nothing should be tried at home. Go to a veterinary clinic right away and say when the legs weakened, how your cat is breathing and whether it has heart disease.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Heart disease Heart A general name for conditions in which the heart can no longer pump blood properly: the heart muscle, the valves or the heart's rhythm can be affected, and some defects are present from birth. In cats heart disease can stay hidden for a long time, so it sometimes comes to light only once it has advanced.
- Hypertrophic cardiomyopathy Heart A disease of the heart muscle in which the wall of the heart slowly thickens, so the heart fills with blood less easily and pumps it less well. It can go unnoticed for a long time, and the signs sometimes appear only once it has advanced. For cats it matters because it can affect breathing and circulation.
Body systems: Heart