Femoral nerve is tested by which reflex, and injury at the level of the femoral triangle would spare which specific muscle group compared to a lesion at the inguinal ligament level?

• A Knee jerk; sartorius and pectineus would be spared
• B Knee jerk; iliopsoas would be spared since it is innervated before the inguinal ligament ✓
• C Ankle jerk; hip flexors would be spared
• D Knee jerk; adductors would be spared

Explanation

The femoral nerve (L2, L3, L4) gives branches to iliopsoas in the iliac fossa before it passes under the inguinal ligament. Therefore, a lesion at the inguinal ligament or femoral triangle level spares iliopsoas (hip flexion remains largely intact) but paralyzes quadriceps femoris (knee extension) and weakens sartorius and pectineus. A lesion proximal to the inguinal ligament would additionally paralyze iliopsoas. The knee jerk (patellar reflex, L3-L4) tests the femoral nerve. Adductors are supplied by the obturator nerve.

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

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