Which nerve extends from the knee down to supply the middle of the leg and the heel?

The nerve that extends from the knee down to supply the middle of the leg and the heel is the tibial nerve. This nerve branches from the sciatic nerve and travels down the back of the leg, providing motor function to the muscles of the posterior compartment and sensory innervation to parts of the foot, including the heel.

The femoral nerve primarily supplies the anterior thigh and does not reach the lower leg, while the saphenous nerve is a branch of the femoral nerve that provides sensation to the medial aspect of the leg, but it does not supply the heel. The radial nerve is involved in the function of the upper arm and forearm and has no role in the innervation of the leg. Thus, the tibial nerve is the correct and only option that fits the description of supplying the middle of the leg and heel region.