A Guide To Lower Extremity Muscle Testing

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Author(s): 
Eric Fuller, DPM

Other Muscle Testing Tips

Anterior tibial muscle. The anterior tibial muscle has the most leverage to dorsiflex the ankle because of an interesting arrangement of the extensor retinaculum. The retinaculum holds the extensor digitorum longus and extensor hallucis longus much closer to the ankle joint. The subtalar joint axis exits out of the foot close to the talar head, which is very near the insertion of the anterior tibial muscle.

   However, with abduction or adduction of the forefoot, the insertion can move relative to the subtalar joint axis. Accordingly, when the forefoot is abducted, the insertion of the tendon can end up lateral to the subtalar joint axis and tension in the tendon will tend to pronate the subtalar joint. When the forefoot adducts, the insertion will be medial to the subtalar joint axis and the anterior tibial muscle can be a supinator of the subtalar joint in this position.

   Testing of the anterior tibial muscle occurs by resisting dorsiflexion of the ankle joint.

   Extensor hallucis longus and extensor digitorum longus. Both of the long toe extensors pass close by but anterior to the ankle joint so they will weakly dorsiflex the ankle. These tendons are lateral to the anterior tibial tendon so they will be more pronators and less supinators than the anterior tibial tendon. The exact action depends on the location of the forefoot in the same manner that the position of the forefoot affects the anterior tibial tendons’ effect at the subtalar joint. The easiest way to test the strength of these muscles is to have the patient dorsiflex the toes while one attempts to plantarflex the metatarsophalangeal joints.

   Dr. Fuller is in private practice at Berkeley Foot Specialists in Berkeley, Calif. He is board-certified by the American Board of Podiatric Medicine.

Reference
1. Scott SH, Winter DA. Internal forces of chronic running injury sites. Medicine Sci Sports Exer. 1990; 22(3):357‑69.

   For further reading, see “Conducting A Quick And Easy Functional Lower Extremity Exam Of An Athlete” in the June 2013 issue of Podiatry Today.

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