Biomechanical evaluation of two clinical tests for plantar heel pain: The dorsiflexion-eversion test for tarsal tunnel syndrome and the windlass test for plantar fasciitis

Background: Plantar heel pain may result from several conditions such as tarsal tunnel syndrome (TTS) and plantar fasciitis. The dorsiflexion-eversion test is used to diagnose TTS, whereas the windlass test is used for plantar fasciitis. Given the similarity between both tests, the purpose of this study was to evaluate whether these tests are able to selectively load the structures which they aim to examine. Methods: Both tests were evaluated in six cadavers by measuring strain in the plantar fascia, tibial nerve, lateral plantar nerve (LPN), and medial plantar nerve (MPN) using miniature displacement transducers. Longitudinal excursion of the nerves was measured with a digital caliper. Results: With the dorsiflexion-eversion test, dorsiflexion and eversion of the ankle in combination with extension of the metatarsophalangeal (NITP) joints significantly increased strain in the tibial nerve (+1.1%), LPN (+2.2%), and MPN (+3.3%) but also in the plantar fascia (+1.2%) (all: p = 0.016). Both components (dorsiflexion-eversion and MTP extension) resulted in significant increases. With the windlass test, extension of all MTP joints significantly increased strain in the plantar fascia (+0.4%, p = 0.016), but also in the tibial nerve (+0.4%, p = 0.016), LPN (+0.8%, p = 0.032) and MPN (+2.0%, p = 0.016). Excursion of the nerves was always in the distal direction but only reached significance for the tibial nerve (6.9 mm, p = 0.016) and LPN (2.2 mm, p = 0.032) during the dorsiflexion-eversion test. Conclusions: Both tests mechanically challenge various structures that have been associated with plantar heel pain. This questions the usefulness of the tests in the differential diagnosis of plantar heel pain.