For 25 years I had a bum knee after a skiing accident. I tore it up and went to the emergency room and they told me it was sprained. Over the years I had x-rays but nothing showed. I ran a lot and to do so, I had to wrap my knee. It was tough walking down stairs as sometimes my knee would just give way a bit. Finally, it gave out when I was walking down the stairs and I fell down about15 stairs on the back of my head. After I got stitched up, I got my knee checked again but this time I had an MRI and it showed my ACL and meniscus were heavily damaged. I had an operation and now my knee feels like new.