Last night I was lying in bed when I heard several thunks on the steps and then Cooper crying. I don't know how he did it, but he managed to fall down the basement steps. This morning he could barely walk so we headed to the vets office. Luckily he didn't break anything. The problem appears to be that the fall aggravated his tumor, so he is in a lot of pain. He's now on serious pain meds and seems to be doing better. I just hope I never have to hear the sound of a dog falling down the stairs again.