Which nerve root primarily supplies sensation to the medial leg and foot?

• A. L3
• B. L5
• C. S1
• D. L4

Answer: (D)

Sensation in the medial leg and foot is mapped to the L4 dermatome. The L4 nerve root supplies cutaneous innervation to the medial aspect of the leg down to the medial malleolus, with the saphenous nerve (a branch of the femoral nerve carrying L4 fibers) delivering sensation to this region. That’s why tapping or touching the medial leg near the shin and ankle most strongly reflects the L4 distribution. In contrast, L3 tends to cover more proximal areas like the thigh/knee, L5 the dorsum of the foot and web space between the first and second toes, and S1 the lateral foot and plantar surface. So the medial leg and foot region being primarily L4 aligns with both the dermatome map and the path of the saphenous nerve.