What Causes Pain And Numbness On The Foot And Toes After Falling Down?

hi I'm a 27 yr old female not over weight or anything but I fell and landed on my knee a few yrs ago and it has hurt ever since but recently when it starts hurting really bad my toes and foot start to tingle and even go numb sometimes. I was wondering what could cause this and do I need to get treatment of some sort?