The weakness of the cat’s hind legs and the collapse of the lumbar spine may be caused by injury, nerve damage, lumbar vertebrae rupture, or other reasons. You need to take the cat to the pet hospital for examination immediately to confirm the cause and treat it promptly to avoid delaying the condition and causing the cat to suffer lifelong consequences. paralysis. Pay attention to the cat's body at ordinary times, help the cat replenish calcium, and do not let the cat jump from too high a place to avoid injuries or fractures.