Which nerve is primarily responsible for motor function to the iliopsoas and for L1-L3 dermatomes?

Which nerve is primarily responsible for motor function to the iliopsoas and for L1-L3 dermatomes?

• A. Femoral
• B. Peroneal
• C. Saphenous
• D. Sciatic

Answer: (A)

Hip flexion via the iliopsoas is driven mainly by the femoral nerve, which carries motor fibers from the L2 to L4 levels to the psoas major and iliacus (and also to the quadriceps to some extent). As it travels into the thigh, the femoral nerve provides sensory fibers that map to the anterior thigh region corresponding to the L2-L4 dermatomes, with the saphenous branch extending the sensory area medially down the leg. This combination—motor to the iliopsoas and sensory coverage of the L1-L3 (groin and anterior thigh) region—fits the femoral nerve best. The other nerves listed don’t innervate the iliopsoas or match this dermatomal distribution: the peroneal and sciatic nerves supply different muscle groups and regions, and the saphenous nerve is primarily sensory.

Hip flexion via the iliopsoas is driven mainly by the femoral nerve, which carries motor fibers from the L2 to L4 levels to the psoas major and iliacus (and also to the quadriceps to some extent). As it travels into the thigh, the femoral nerve provides sensory fibers that map to the anterior thigh region corresponding to the L2-L4 dermatomes, with the saphenous branch extending the sensory area medially down the leg. This combination—motor to the iliopsoas and sensory coverage of the L1-L3 (groin and anterior thigh) region—fits the femoral nerve best. The other nerves listed don’t innervate the iliopsoas or match this dermatomal distribution: the peroneal and sciatic nerves supply different muscle groups and regions, and the saphenous nerve is primarily sensory.