I had my left knee replaced 01/04. I had my left knee replaced 6 weeks later 3/04. I was quite pleased with the way my knee were responding until April 2005. I rolled over in bed and had what felt like and explosion in my left leg. The polyethylene tibial post had sheared off. We got in an saw my OS as soon as possible. The broken piece of poly floated inside my leg for about 4-6 wks before my OS could operate on remove it and do a poly exchange. After surgery my knee never got to feel right. I had alot of pain and instability for the next 3 years. In August 2008 I was at my OS office because of the pain and instability. He manipulted my leg to try and get it do do what I complained about for the last 3 years. Finally he moved it and it dislocated, he decided that I was jumping the post. He scheduled surgery for Sept 22 2008. Upon opening me up he discovered that the post had sheared off again and that the post had incapsulated itself behind my knee. Has anyone hd their tibial fracture or shear off.