Hip adductor weakness would most likely reflect involvement of which nerve roots?

• A. L4, L5
• B. L2, L3, L4
• C. S1
• D. L5, S1

Answer: (B)

Hip adductor weakness points to involvement of the nerve roots that supply the main hip adductor muscles. The major hip adductors (adductor longus, adductor brevis, and the adductor part of adductor magnus) are innervated by the obturator nerve, which carries fibers from L2, L3, and L4. If there’s a problem at these roots, the motor strength of hip adduction drops because the primary adductor muscles can’t receive their normal signals.

In contrast, the hamstring portion of adductor magnus is innervated by the tibial branch of the sciatic nerve (L4-S1), so issues at those lower levels don’t produce as clean a deficit in hip adduction. Lesions affecting L5-S1 or L4-L5 would tend to show weakness in different muscle groups, not the classic hip adductors. Hence, the pattern most consistent with hip adductor weakness is involvement of L2 through L4.