It is not a figment of your imagination. My pt or even myself usually work my legs to they are fried. Of course, long term this builds muscle and endurance. However, the rest of the day after a tough workout, I do have potential buckling issues. Other qtr.'s have had this issue also. Pay attention to your body, it will tell you when to slow down as well as when to proceed. I just returned from a business trip to San Francisco. It went well, but you have good and bad days. I am blessed to have come this far, but it will be another 2-3 months I think before the strength and confidence is there. My gait is still not where it was and it is not consistently the same either. It is frustrating, but I see the light and all things get a little better each day(excluding the bad days/moments). When you first stand up, sometimes I just let everything settle before walking, stiffness and soreness seems to go away as you walk. I walked a country mile or two during my trip and everything was fine, but I still watch my steps, careful on slopes and am a little over cautious at times.