I have this big cashmere whether who weighs about 110 pounds. Every time he takes a step, his front knees make a loud cracking noise. If he steps with his right leg it cracks, and vice versa. He is about five and has done this for as long as I have had him constantly. It doesn't seem to bother him in the least, I was just wondering if anyone knew what causes it? I thought maybe it was just because he was stiff, but always happens even if he has been up walking around all day. I can tell it's the joint of his front knees doing it. Any ideas as to what this is would be appreciated!!