Which physical exam findings are characteristic of mechanical back pain caused by herniated discs?

Updated: Aug 27, 2020
  • Author: Debra G Perina, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Patients with true herniated discs may not present with any findings other than a positive straight leg raising test. Classic presentation includes numbness in a dermatomal distribution corresponding to the level of disc involved, with findings of motor weakness and reflex loss as described below. Herniated discs have different presentations depending on the location as follows:

  • At L4: Pain along the front of the leg; weak extension of the leg at the knee; sensory loss about the knee; loss of knee-jerk reflex

  • At L5: Pain along the side of the leg; weak dorsiflexion of the foot; sensory loss in the web of the big toe; no reflexes lost

  • At S1: Pain along the back of the leg; weak plantar flexion of the foot; sensory loss along the back of the calf and the lateral aspect of the foot; loss of ankle jerk

  • L5 and S1: These nerve roots are involved in approximately 95% of all disc herniations.

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