Had RK microfracture & LK OATS. Somewhat able to do things with tolerable pain level. Started back with the floor pilaties & yoga. Too much stretching I guess. I started where you are with similiar discomforts. Then started to hurt behind the knee and on the lateral side. Now...I can't stand without both knee fatique and pain, i can't walk without pain. It has ruined me! I'm walking with braces and oh boy if i have to go up or down stairs, HELP~! Back to a new OS, more Xray's & 2 MRI's one on each knee. The OATS failed on the left knee. I have defects in both knees. 2nd OS said too young at 50 for TKR. Going Monday to 3rd OS for possible injections and PT. If I can get back to a tolerable level of pain I swear I will never do those demanding moves of yoga and pilaties again. Be very careful as I didn't think much of the pain when first started. Hopefully yours will not get worse.
I am sorry you have had such difficulty with your knees. My right knee seems to be getting better - I am being very careful with it. I stopped exercising for a week, but I have started back taking my Pilates and yoga classes. If something is uncomfortable, I just pass on it. Hopefully, whatever it is will heal itself.
Unfortunately, it is imposible to make a diagnosis from this simple description. If your pain is persistant, and does not respond to a short period of rest or activity modification, then I would suggest evaluation by an orthopedist.
At that time, your doctor will take a thorough history, examine your knee and entire lower extremity, and use xrays and MRI if necessary, to formulate a diagnosis.
After a dianosis is reached, then a treatment plan that makes sense for you canbe instituted.