What are the AMA Guides to the Evaluation of Permanent Impairment and how are they used to evaluate patients with mechanical low back pain?

Updated: Mar 30, 2020
  • Author: Everett C Hills, MD, MS; Chief Editor: Stephen Kishner, MD, MHA  more...
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The AMA Guides to the Evaluation of Permanent Impairment (5th edition) include reference tables for all motions, but these figures are not based on empiric data, only on consensus. [22] The ROM measurements in the AMA Guides do not correlate with disability and are not consistent within the document itself.

Palpate the entire spine to identify vertebral tenderness that may be a nonspecific finding of fracture or other cause of low back pain (LBP). Note any asymmetry, misalignment, or step-off between vertebral bodies. Remember also to palpate the sacroiliac joints.

Test for manual muscle strength in both lower extremities. The Medical Research Council rating is an ordinal scale used for this purpose (0 = absent strength, 1 = trace muscle movement, 2 = poor muscle strength [less than antigravity], 3 = fair muscle strength [antigravity strength through normal arc of motion], 4 = good strength, and 5 = normal strength).

Table 1. Functional Muscle Testing (Open Table in a new window)

Nerve Root

Motor Examination

Functional Test


Extend quadriceps

Squat down and rise


Dorsiflex ankle

Walk on heels


Dorsiflex great toe

Walk on heels


Stand on toes*

Walk on toes (plantarflex ankle)

*When testing the S1 innervated gastrocnemius muscle, the ability to stand on the toes once represents fair (3/5) strength. The patient must stand on his or her toes 5 times in a row to be rated normal (5/5) strength. Note that this approach should allow the physician to detect weakness at a much milder stage than if gastrocnemius strength were assessed only by using the examiner's hand to apply resistance to ankle plantar flexion.

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