My cat suddenly cannot use its back legs and is crying in pain — what is happening?
Sudden hind-leg paralysis with loud crying in a cat is the classic picture of an aortic blood clot — one of the most painful feline emergencies, and one where every hour counts.
The clot, often called a saddle thrombus, usually forms inside a diseased heart and then lodges where the aorta splits toward the hind legs, abruptly cutting off their blood supply. Affected cats drag cold, stiff back legs and vocalize from pain.
How to recognize it and what to do
Check the paw pads and nail beds: on the blocked side they turn pale or bluish and feel colder than the front paws, and the muscles of the affected legs harden. Many owners first suspect a fall or a broken bone, but a fracture rarely affects both hind legs at once or makes the pads lose their color.
Underlying heart disease and how much muscle damage the cat can tolerate differ between individuals, and pain relief plus clot management must start quickly to keep options open. Do not massage or warm the legs at home; wrap the cat loosely in a towel, keep it as calm as possible, and go to an emergency veterinary hospital immediately, calling ahead on the way.
MediIndex articles are for general information only and are not medical advice, diagnosis, or advertising. Outcomes vary by individual — consult a board-certified specialist for personal decisions.