I am a young 69 year old female, and I have the very same problem. I had back surgery two years ago and knee surgery 4 months ago. I had this issue right after back surgery, but after physical therapy, it got better. I have tried to walk recently, and the issues have returned. I could not walk during the summer due to the horrible weather. I have put on weight, and I wonder if that is the problem? This is totally new to me, and I have been physically active all my life.