Oh, climbing poles with those spiked shoes? That is really stressful on the legs and feet! Make sure you tell the doctor about that too!

http://en.wikipedia.org/wiki/Common_fibular_nerve
This site shows the nerve behind the knee in a diagram.

I have compression behind my rt knee from this, when it flares up I cannot put weight on my leg. I use Lidoderm patches for it and it goes away in a day or two. I've had minor dislocations of that knee in the past... it hurts like devil and takes your breath away!

As we age the cartilage in the knees wears thin. So that strange movements can pull it out of line. Sitting with legs hooked on a chair or a stool (like kitchen or bar stools), is one way to pull it out. Another is twisting motions while standing and keeping the feet firm and not rotating them with the leg. It can happen more easily when you are older than younger.

There is a stretch a chiropractor taught me to help realign the knee. Put your leg up on a low stool, or low step about 24 in high, toes pointing up, and keep the heel from moving and pull back to stretch the hamstrings (back of leg) ...hold for a few seconds, and repeat. If you feel a click or pop of any kind then your knee is moving and you don't realize it. Hanging that leg out may have pulled it slightly --enough to bother that nerve.

I'd avoid the runner's stretch where you pull your leg behind you grab with your hand. That will compress the nerve considerably.

drawings:
http://www.google.com/imgres?imgurl=...9QEwBQ&dur=295

The first one on the right top row, is the stretch I do for my knee. I pulls it straight if it is off center. (back of thighs)

The first drawing on the LEFT in second row, is the runner stretch, I'd avoid with compression of the peroneal nerve behind the knee. (front of thighs).