Set oven control to broil. Place pork ribs on broiler pan. Broil with top about 6 inches from heat 12 to 14 minutes, turning once, until lightly browned.
Spray 3 1/2- to 4-quart slow cooker with cooking spray. In cooker, place onion, carrots and celery. Place pork on vegetables. Pour pasta sauce over pork; sprinkle with salt and pepper.
Cover; cook on Low heat setting 7 to 8 hours.
About 15 minutes before serving, make polenta as directed on package. Place polenta on individual serving plates; serve with pork and sauce.