Which nerve roots innervate the iliopsoas muscle?

Which nerve roots innervate the iliopsoas muscle?

• A. L2-L4
• B. L1-L3
• C. L4-S1
• D. L3-L5

Answer: (A)

The hip flexor iliopsoas is made up of two muscles with slightly different nerve sources. Psoas major gets innervation from branches of the ventral rami of the lower lumbar nerves L1 through L3. Iliacus receives innervation from the femoral nerve, which carries fibers from L2 through L4. Since the iliopsoas as a whole relies on both sources, the combined nerve root range that can innervate it spans from L2 to L4. L2 and L3 are common to both parts, and L4 comes in via the femoral nerve to iliacus, widening the range. The other options fall short because they miss part of the actual supply: one omits L4, another omits L2, and another begins too late to include L2-L3.

The hip flexor iliopsoas is made up of two muscles with slightly different nerve sources. Psoas major gets innervation from branches of the ventral rami of the lower lumbar nerves L1 through L3. Iliacus receives innervation from the femoral nerve, which carries fibers from L2 through L4. Since the iliopsoas as a whole relies on both sources, the combined nerve root range that can innervate it spans from L2 to L4. L2 and L3 are common to both parts, and L4 comes in via the femoral nerve to iliacus, widening the range.

The other options fall short because they miss part of the actual supply: one omits L4, another omits L2, and another begins too late to include L2-L3.