How can you bias the tibial nerve during SLR testing?

To effectively bias the tibial nerve during a straight leg raise (SLR) test, the specific position of the ankle is crucial. Dorsiflexion and eversion of the foot are key as they increase tension on the tibial nerve.

When the ankle is in dorsiflexion, the overall length of the tibial nerve increases. Eversion, on the other hand, places additional strain on the tibial nerve by influencing its path through the tarsal tunnel, where it branches into the medial and lateral plantar nerves. This biomechanical adjustment alters the tension on the nerve, making it more likely to elicit symptoms associated with tibial nerve irritation or entrapment, such as pain or paresthesia.

In contrast, the other combinations of ankle positioning—plantarflexion, inversion, or their various combinations—do not appropriately target the tibial nerve in a similarly effective manner. Plantarflexion, for instance, would generally reduce tension along the tibial nerve rather than increase it. Therefore, implementing dorsiflexion and eversion during the SLR raises not only creates the suitable tension gradient needed to adequately assess tibial nerve function but also allows for better identification of potential nerve pathologies.