Cartrophen
Cartrophen is an injection that helps arthritis.  Cartrophen is not cortisone and it is not carprofen (a pain relief medicine).  It is a disease modifying osteoarthritic drug and is the only drug in the class (some copycat drugs have come out e.g. Pentosan and Sylvet but they are not as good). 
It is most beneficial when given by injection once a week for 4 weeks.  It is very effective in joint problems.  It increases the enzymes in the synovial fluid in the joint.  This helps the cartilage to heal. 
Cartrophen can be used at the same time as pain relief meds e.g. Rimadyl, Metacam or cortisone.  It works best when combined with glucosamines and chondroitin. E.g. Seaflex, Arthrocart. It can also be used with omega 3 oil supplement.
 Also Cartrophen:

• Stimulates synthesis of normal synovial fluid
• Inhibits enzymes that degrade cartilage
• Increase cartilage matrix replacement
• Mobilises blood clots and fibrin deposits and improves blood perfusion in joints

 Cartrophen is a very effective drug that treats the disease itself and not just the symptoms. 
There have been trials in people at Royal North Shore Hospital Sydney, P. Gosh et al 2005.  A pilot study found significantly improved joint function, joint stiffness and pain compared with control group with osteoarthritis of knees. (Curr Ther Res Clin Exp 2005:66:552-571)
 Studies show reduced joint inflammation, improved blood flow in subchondral bone and soft tissue and preserved proteoglycans and hyaluronidase concentrations in articular cartilage and synovial fluid.  Cartrophen is a very good option for arthritis relief. 
If this does not give adequate results then it is best to consider stem cell therapy or surgery.  Discuss options with your vet or vet nurse.