I am using cosequin plus chewables here for Jazz, they have glucosamine, chondroitin and Msm in them, but no vitamin c like the regular cosequin does. Sometimes she holds her leg up, vet thinks that she is in early stages of knee issues.
The joint supplements do help with knee pain, and hyaluronic acid added I think helps more. I knew a gsd owner that injected glucosamine. It won't change any of the grovve, but it will lubricate the joint and help with the pain.
I would not use the tail to hold up the dog, you can cause nerve damage at the base of the tail.