My dog (actually my fiance's) is about 10 years old. He adopted him from the humane society when he was a puppy. We have just started noticing that his back legs are looking weak and it seems as though the muscle mass is deteriorating. He has also started whimpering when he is laying down and sometimes while he is sleeping. We started giving him glucosamine/chondrointin supplements a few months ago to try to slow the cartilage deterioration but we haven't noticed any change. Today, I noticed that he is now limping and holding up his front paw like he stepped on something sharp but I inspected it intensly and found nothing. We are taking him to the vet this week but I am scared. This is the first dog I have ever been around and I love him. Has anyone ever had their dog go through something like this? My fiance isn't home today and I am debating on whether or not to take him to an emergency clinic.