Testing the patellar reflex assesses the function of which nerve?

Testing the patellar reflex assesses the function of which nerve?

• A. Obturator nerve
• B. Femoral nerve
• C. Sciatic nerve
• D. Tibial nerve

Answer: (B)

The knee-jerk (patellar) reflex mainly tests the femoral nerve pathway to the quadriceps muscle. When the patellar tendon is tapped, the quadriceps muscle is stretched, and a signal travels from the muscle spindle through the femoral nerve into the spinal cord at the L2–L4 levels. A direct, monosynaptic connection then sends a motor impulse back along the femoral nerve to the quadriceps, causing the knee to kick outward. Because this reflex arc depends on the femoral nerve and these L2–L4 spinal segments, its presence and strength reflect the integrity of that nerve pathway. The other nerves aren’t primarily involved in this reflex. The obturator nerve mainly controls thigh adductors, while the sciatic nerve (and its tibial branch) governs muscles on the posterior thigh and lower leg. Dysfunction in those nerves wouldn’t produce the classic patellar reflex response, which is why the femoral nerve is the best answer.

The knee-jerk (patellar) reflex mainly tests the femoral nerve pathway to the quadriceps muscle. When the patellar tendon is tapped, the quadriceps muscle is stretched, and a signal travels from the muscle spindle through the femoral nerve into the spinal cord at the L2–L4 levels. A direct, monosynaptic connection then sends a motor impulse back along the femoral nerve to the quadriceps, causing the knee to kick outward. Because this reflex arc depends on the femoral nerve and these L2–L4 spinal segments, its presence and strength reflect the integrity of that nerve pathway.

The other nerves aren’t primarily involved in this reflex. The obturator nerve mainly controls thigh adductors, while the sciatic nerve (and its tibial branch) governs muscles on the posterior thigh and lower leg. Dysfunction in those nerves wouldn’t produce the classic patellar reflex response, which is why the femoral nerve is the best answer.