Suggest Treatment For Sharp Pain In Knee With Numbness In Toes

I've had a sharp pain in the back of my knee/lower thigh area for a while now. It hurts more when I'm sitting & there's pressure against the back of my knee/thigh, and I get numbness and tingling sensations in that leg frequently, as well as my toes going numb (my fingers have a tendency to go numb and colorless as well.) Any advice?