I just found the site, and seems to have a lot of information. I thought I injured my knee in 2001 while in the Marine Corps. Was diganosed with patellafemoral syndrome, and was looked at by about 4 or 5 doctors. None of which botherd to look at my back. In 2003 I got out the Corps and went home, at that time I could stand for about 8-10 hours with little pain. By 2007 I was able to stand/walk for about 10 minutes and then had large amounts of pain through the hip, knee, thigh, and the finally making my foot tingle. I was seen by two other doctors and finaly sent to see a physiotherapist. I gave him the same story of the injury as the other, he took some pictures and let me know my knee was fine. After 9 months of physio 2 times a week my pain had not went away and I requested aback X-Ray. That is when I finally found out why I had pain. L4-L5 pars defect/fracture with grade 2 spondylolisthesis, root compression, and spinal instability. Had a nerve block done about 9 months ago and the pain has been coming back over last 3 months.