glucosamine supplement questions...

I have a few questions that someone on IP should be able to answer. As soon as I adopted Titus I noticed that he was always popping or cracking. At the time not know whether the sounds were coming from his knees or his hips I knew it wouldn't hurt anything to start him on glucosamine chondroitin supplements. He hated them, would spit them out the second I'd turn my back. I thought maybe he didn't care for that flavor so I went and bought another brand and flavor only to get the same result. It didn't matter that the pills were chewable or if they were in cheese, PB or canned food. Shortly there after he began locking his jaws so that I couldn't even attempt to force the supplements down his throat. Are human grade glucosamine and chondroitin supplements safe for dogs? The only reason that I'm entertaining this thought is that they are not flavored and many come with some sort of gel coating. With his recent diagnosis of a torn ACL and arthitic knee I know it's important to get him back on these supplements. I know that this is a question that I should have asked the vet but didn't think about it there. He's currently eating Blue lamb and rice, we may switch to the senior chicken and rice formula for the extra G&C supplements that are supposed to be in there. Thanks, Lynn