Question

S1 and S2 nerve roots are checked by which reflex?

• A. Knee jerk
• B. Patellar reflex
• C. Calcaneal reflex
• D. None

Hint:

S1-S2 maps to the ankle jerk, also known as the Achilles reflex.

Answer 1

The Correct Option is C

Step 1: Deep tendon reflexes are used clinically to test specific spinal nerve root levels. Each reflex maps to a defined root.

Step 2: The ankle jerk, also called the calcaneal reflex or Achilles reflex, is elicited by tapping the Achilles tendon and tests the S1 and S2 nerve roots through the tibial nerve and gastrocnemius-soleus contraction.

Step 3: The other options test a different level. The knee jerk and the patellar reflex are the same reflex (the patellar tendon jerk) and they test the L2, L3 and L4 roots, mainly L3-L4, not S1-S2.

Step 4: Therefore S1-S2 is checked by the calcaneal (ankle) reflex, option c.