[pct-l] Knee problems and backpacking

[Joe Bastian]

I was hoping some backpacker on this forum could shed some light on my knee problem as the 2 doctors I've gone to are clueless.
 
After a 3 day hike averaging 20 miles a day I got into my car for the 30min drive home. When I got home my right knee hurt so bad I could barely walk. After about a month and a half of healing my right knee felt better so I went out on another hike for 3 days. On the 3rd day I laid down on the trail for a break and when I got up the same pain was in my left knee. 2 hikers had to carry me out on a strecher. In both cases the injury occurred while I was sitting down and I don't feel anything wrong until I get up to walk again. Luckily this was 1.5 years ago and hasn't happened since.
 
Since I'm planning to thru-hike this year I'm concerned this might happen again. Has anyone ever heard of such a problem?
 
Thanks
 
Confused Joe