What Causes Sudden Numbness In The Knee While Having Restless Leg Syndrome?

I have severe restless legs syndrome for which I have been taking for many years Requip and Klonopin. Last night shortly after taking them but in far less time than I usually feel any effect, a knee would suddenly just fail to hold me when walking and also while walking I felt I might have fainted for a nanosecond and jerked awake. I have never experienced these symptoms before. Are these likely side effects or should I expect some other problem. I didn t take my blood pressure, but it is normally just right, neither, high or low. I am a female age 72 and other than a little osteoarthritis and Shogrens am in perfect health.