My favorite dog was a 65lb flat-coat retriever. As he got older, his hips clearly grew stiff and painful. It hurt him to get up and hurt the first few steps until he 'warmed up'. I found that a single regular strength aspirin, put way back on his tongue to aid swallowing (and who likes the taste of aspirin, anyway?) really made a difference.

I'd give it about three minutes to take effect, and then he'd jump up like a three year old. You should have seen the look of surprise on his face the first time! After that he took the aspirin eagerly.

I guess you should set the dosage by weight. The directions based on the weight of a child would probably be a good place to start. Fortunately, I've only heard of big dogs suffering hip problems. Could you imagine trying to dose a Chihuahua?!