My yellow labrador retriever has been displaying symptoms of arthritis. He has a lot of trouble getting up after a nap, and he has gotten fatter since it hurts him when he runs, which makes it even harder for him to get up. He also walks using three legs. He bends his left leg when he walks, he is obviously in pain. I have been giving him an aspirin every day but now the symptoms have gotten worse and I need something new. Is there anything I can do before taking him to the vet for expensive x-rays and medications?