Abnormal reflex in the right knee during the knee-jerk exam localizes to which spinal levels?

Abnormal reflex in the right knee during the knee-jerk exam localizes to which spinal levels?

• A. Cervical 5 and 6
• B. Cervical 6 and 7
• C. Lumbar 2, 3, and 4
• D. Sacral 1

Answer: (C)

The knee-jerk (patellar) reflex uses the quadriceps via the femoral nerve, and its sensory and motor pathways come from the lumbar spinal cord. The reflex arc runs through the L2 to L4 levels, with L4 contributing most strongly. So an abnormal patellar reflex localizes to the lumbar region, specifically the L2–L4 segments. In contrast, cervical levels would affect arm reflexes (for example, C5–C6), and sacral levels would more likely involve the ankle or plantar responses, not the knee.

The knee-jerk (patellar) reflex uses the quadriceps via the femoral nerve, and its sensory and motor pathways come from the lumbar spinal cord. The reflex arc runs through the L2 to L4 levels, with L4 contributing most strongly. So an abnormal patellar reflex localizes to the lumbar region, specifically the L2–L4 segments. In contrast, cervical levels would affect arm reflexes (for example, C5–C6), and sacral levels would more likely involve the ankle or plantar responses, not the knee.