I agree that to many broken bones happen and also some members have said that dogs can get LP (luxating patella) from this also...better to be safe than sorry.
A number of members have these stairs (4 step set) and I have 4 of them in my house. They are just foam so if you stub your toe it won't hurt.
http://www.lakeside.com/details.asp?...&ST=KWD&SS=SOR