Walking on the hocks is a sign of weakness! She could have a number of conditions such as diabetes, kidney disease, or other electrolyte abnormalities. You should have your veterinarian take look at her and run some blood work ASAP!
how old is she? are you certain its arthritic issues? has she seen a Vet? there are some prescription meds they can prescribe but you need to know for sure what is causing the pain....