Yes, heaviness in legs. My knee will also just randomly give out. Thankfully not real often and I have been able to catch myself. I am not sure where you live, but the cold weather can make it worse. This unusually cold winter has been horrible for me. You also said something about crouching and not being able to get up, I believe. The heaviness in legs, possible weaker muscles, fatigue, and balance issues could all play into that.