A patient develops inability to extend the knee, loss of knee jerk, and sensory loss over the anterior and medial thigh and medial leg. The nerve injured is the femoral nerve. Which compartment of the thigh is most commonly affected if a femoral nerve block inadvertently spreads?

• A Medial compartment (gracilis, adductors)
• B Posterior compartment (hamstrings)
• C Gluteal compartment (gluteus maximus)
• D Anterior compartment (quadriceps, sartorius) ✓

Explanation

The femoral nerve (L2–L4) innervates the anterior compartment of the thigh: quadriceps femoris (knee extension — L3,4), sartorius (hip flexion and knee flexion), and pectineus (hip flexion, adduction). Loss of quadriceps causes inability to extend the knee and absent knee jerk (L3,4). Sensory supply is anterior thigh and medial leg (via saphenous nerve). The medial compartment is supplied by the obturator nerve; posterior compartment by the sciatic nerve; gluteal region by superior/inferior gluteal nerves.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.