My dogs knee still pops out after surgery?

My dog just had a luxating patella knee surgery on Friday and his knee keeps popping out. I'm not sure if it just takes a while to heal or if he needs to be checked out again. He doesn't seem to be in any pain but the whole point of the surgery was so that his knee wouldn't pop out when he walks. I know I should call the vet but I didn't want to be overreacting and worried if its all apart of the healing process. Obviously if I had knee surgery it wouldn't be up to par the very next day, so I'm figuring its like that for dogs as well?

I would definitely check with your vet. When you picked him up from surgery you should have received discharge instructions on the healing process, activity level and all other pertinent information regarding his recovery. The vet or technician should have answered all your questions at that time and he may, or may not, have had a bandage on the knee. Call and ask - if necessary ask if you need recheck appointments to make sure the surgery is healing well also. Something is not right if you are seeing the knee pop in and out at this point. You are not overreacting.

If it was only done Friday, then I'm surprised he is already putting it to the floor. I have never had a dog needing this surgery as it is usually small dogs that suffer, however, logic says that it should not be popping out. I am wondering if the ligaments are now so stretched that it isn't going to stay in place even with deeper grooves. I think you should phone and discuss it tbh.