Left Knee pain; what's the deal?

[vness]

Sit in chair. Move forward so that you are sitting at edge of chair. Extend legs, heels to floor. Keep knees straight (or as straight as possible if you have arthritis.) Tighten thigh muscles. Hold for count of 10. Relax for count of 3. Do 10 repetitions. You can do this several times throughout the day. You can build up to 2 or 3 sets of 10 repetitions at a time.
Hope this will help you.

Hi... can you tell me what the result of doing this exercise is? Besides obviously tightening my quads... I know there's got to be more to it.... and I feel like such a dummy for asking... but if I don't ask, I don't learn :)
thanks
namaste,
v