Herniated Disc (L5–S1): The Daily PANCE Blueprint
A 41-year-old man has 2 weeks of low back pain that shoots down the back of his left leg to the outer edge of his foot. It began after he lifted a heavy box, and coughing makes the leg pain worse. He has no bowel or bladder symptoms and no saddle numbness. You suspect a posterolateral L5–S1 disc herniation compressing the S1 nerve root. Which examination finding would you most expect?
A. Decreased patellar (knee) reflex
B. Decreased Achilles (ankle) reflex
C. Weakness of great toe extension
D. Weakness of hip flexion
E. Decreased sensation over the medial lower leg
Answer and topic summary
The answer is B. Decreased Achilles (ankle) reflex
A posterolateral L5–S1 herniation compresses the S1 root. S1 findings are a decreased or absent Achilles reflex, weak plantar flexion (trouble walking on the toes), and numbness of the lateral foot and sole. Learn the three common roots as a set. L4: decreased patellar reflex, weak knee extension, and numbness over the medial lower leg. L5: weak great toe extension and ankle dorsiflexion (trouble walking on the heels), numbness over the top of the foot, and no reliable reflex. Hip flexion is mainly L2 and L3. A positive straight-leg raise between 30 and 70 degrees supports nerve root irritation. Most disc herniations improve within 6 weeks with NSAIDs and staying active, and imaging is not needed at first. Order an urgent MRI for red flags: saddle anesthesia, urinary retention, or bowel incontinence (cauda equina syndrome), or a worsening motor deficit.
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