We had a calf who had a bad case of this probably five years ago. In addition to the medication, we also fed the calf with a tube a couple times a day, early on, since the calf wasn't getting up to nurse very much. It takes a lot of dedication to make sure that you give them their medication on schedule but don't give up, these calves can be saved (though I've had some folks tell me otherwise).
Our vet also encouraged us to massage the sore knees. So whenever we handled the calf to feed it or give shots, we would also spend a few minutes rubbing the knees to promote circulation. I have no idea if it helped, but the calf eventually got better and became a mama cow in the herd.
Good luck!