(e) Achilles reflex (ankle jerk). Tap the Achilles tendon and the foot
should extend from the contraction of the gastrocnemius and soleus muscles
responding to that tap. Perform the reflex test in this manner:
1 Have the patient sit on a table or bed so that his legs dangle.
2 With your left hand, grasp the patient's foot and pull it in
dorsiflexion (upward). Find the degree of stretching upward of the Achilles tendon that
produces the optimal response.
3 Tap the tendon directly.
4 Normal response is contraction of the gastrocnemius and
plantar flexion of the foot.
If the normal response does not occur, there may be damage to the nerves
supplying the posterior leg muscles or damage to the nerve cells in the
lumbosacral region of the spinal cord. Individuals who do not have this
response (the ankle jerk) include persons with chronic diabetes,
neurosyphilis, alcoholism, and subarachnoid hemorrhages.
Figure 2-13. Achilles reflex (ankle jerk).
5 If the patient must be in the supine position, perform the check
in this manner. Partially flex the hip and knee, then rotate the knee outward as far as is
comfortable for the patient. With your left hand, grasp his foot and pull the foot upward.
Tap the Achilles tendon directly. The normal response is plantar flexion.