Yep, Jan the exact same thing happened to me with my knees that I did not even know had severe arthritis in them. My ortho Dr also got me out of mine. Funny thing was I also belonged to another gym that I went to faithfully 5-6 days a week for 1-2 hours using low impact treadmill up to 3.5 mph for an hour at a time and thanks to curves I now can't even do that anymore. I have to start from scratch and start pool walking!