Never. On all fours better. Long time ago my neighbor's cat fell from 6th floor outside on the pavement and he broke all 4 of his legs but survived. She was advised to feed him nothing but raw grounded beef and she did. He became fat and he was limping but eventually was all right. The poor guy just wanted some fresh air, didn't he? Talking about 8 lives of a cat! This cat definitely had couple more to spare.