My horse has osteoarthiritis and degenerative joint disease, what can I do?

My horse has been diagnosed with mild osteoarthiritis and degenerative joint disease in his right stifle. The vet recommended additional screening at a surgical clinic and starting him on bute and cosequin ASU. I need to call the vet and get further clarification on her recommendations. Does anyone have experience with this, and had any luck with supplements, remedies, shots that helped. Will I be able to ride him again? He is an 18 year old thoroughbred. thanks!