Q: Is hardwood too slick for a large dog with bad hips?
A: I don’t think so. There are finishes that offer non slip such as from Basic Coatings. Also, some gloss finishes tend to be less slippery than semi or satin. You could put down a runner in the main areas where the dog walks. I think dogs adjust to what they are walking on, and it sounds like your dog is not a puppy so is not extremely active. He probably would like laying down on it on hot days rather than carpet.