Josephine,
Over the past 4 years my knees have popped, really loud, and and my left knee would feel like it was going to float out from under me and sometimes if I stood in one place too long it would lock up and I would have to move it around and it felt like it would pop back into place. Left knee has never felt quite right. Still had problems going up and down stairs. It always felt like it was going to get to the bottom before the rest of me did.
The doctor I went to specializes in knee revisions and he said the knees should not be as loose as mine was. When he moved them around it felt as if they were not attached to anything. Scary feeling! I was experiencing pain on the left knee mostly when I was laying down and the pain would wake me up. And it is still hurting at night even more.
He said the poly was not worn, it just wasn't thick enough. He said the appliance was secure so he chose to go with just replacing the poly with 10mm. He said it's the same in my right knee and I am scheduled to have it done in May.
The pain on LF3 and LF4 hurts the most from C,D,E, but at times the pain will go down my shin and up my thigh. On LB4 and LB3 it seems to stay right around the C, D, E area.