Anybody know wtf just happened to my leg?

Occasionaly my leg goes straight when i walk. but its only once.

well i just got off the couch a few min ago to unlock the door for my sister. my leg straightened again. no big deal, i continues walking, it happens again, i ignor it, but once i get by the dining table, it hapens again and i fall. i get up , seriously freaked out, and walk again slowly. it happens and i fall again. Skylar has no idea wat the hell is going on. i finally open the door and she ever so kindly help me up and help me walk to the couch again just in case i fall. (or she was wanting to see me fall on my ass again )

Anybody know what happened? im not sure how to explain the leg straightening thing that well.

Thanks!