I had lower back surgery almost two years ago due to an old sports injury -- part of disc had separated and was pressing on nerve. Before surgery, aside from being in horrible pain, I experienced numbness in my lower left leg. After recovering from surgery, all was good -- I've gone skiing, played sports, etc. I've been thankful. But today, after doing a bunch of outdoors work, I sat down with my leg pressed against a stool. My left leg shook uncontrollably. No pain. My right leg was fine. I can't help but think it is related to previous issues described above. Thoughts?