believe me,i am the queen of strange and insane body stuff ever since my spinal cord was injured. i can relate to what you are describing. the one thing that would really be helpful in pinpointing the root of your problem would be an MRI, done on your whole spinal area. just to see if there is something inside there that is causing this, it would be the 'most likely' place to start. have you ever seen at least your primary about this stuff? having just a consult/eval with him or her and getting that referral for the MRI would at least be a good starting point. its just not normal to have your legs do that,as i know you already know.
if you do indeed have some level of "hightened" reflexes of responses in your legs,it could be coming from just about any level of your spine. it all depends upon just what it actually is that is affecting things and where it is located. but you DO need to get this better evaled at this point. your doc would do a basic neuro eval which would include tapping your knees withthe little hammer? this one test would show if your reflexes are too hyper. mine are and believe me,my legs do their little "happy dance" at various times thru out my day.
i would simply make an appt with your primary for that eval and see about getting that MRI. 'something" is causing this to occur in you and just needs to be found out. an MRI,with a contrasting agent will hopefully show that for you. it could be many possible things that could be affecting certain areas,so i am not EVEN goin there right now. just push for the MRI. good luck and please keep me posted as to what you find out. FB