Name of test

Ankle plantar flexion

What it tests

Function of gastroc-soleus complex

How to do it

Have patient actively plantar flex the ankle (black arrow) against resistance (red line)

The normal response

Strong plantar flexion. Note that active plantar flexion against manual resistance can seem strong to the examiner’s hand even with true weakness (relative to normal demands). That’s because the legs are typically so much stronger than the arms.

Also, a reasonable amount of plantar flexion strength may be seen even with a complete Achilles rupture as the posterior tibialis and toe flexors powers plantar flexion motion too.

What it means if not normal

True weakness could reflect primary muscle weakness, tendon rupture or nerve pathology (sciatic in general, tibial nerve specifically, or nerve roots S1 or S2)

Achilles tendon pathology causing pain may lead to guarding and apparent weakness.

Comments

Best done as a series of toe-rises (stepping down on the forefoot to elevate the heel, shown in the second figure), as subtle weakness will not be apparent on manual testing. A normal patient should be able to elevate off the ground (green arrow) ten times consecutively without fatigue. A lack of tenderness to palpation along the Achilles should exclude tendinopathy.

Citations

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Figures

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