Why is a sciatic nerve block necessary for adequate anesthesia for a total knee arthroplasty?

Why is a sciatic nerve block necessary for adequate anesthesia for a total knee arthroplasty?

Firstly, most orthopedists utilize a thigh tourniquet for the total knee arthroplasty to minimize blood loss. Without the sciatic nerve block, the posterior thigh would not be anesthetized. Secondly, although there is a trend in the orthopedic world to minimize the incision for a total knee arthroplasty, it may still extend into an area below the knee that is not innervated by the femoral or saphenous nerves. Thirdly, drilling into the anterior knee may reach posterior portions of the knee which are not innervated by the femoral nerve.