Jacks Test is a test of how hard it is to dorsiflex the hallux when weightbearing, so is a test of the integrity of the windlass mechanism. It is known at the Hubscher maneuver in the USA

Jack’s test is a clinical examination used to assess the function of the medial longitudinal arch of the foot, particularly in evaluating for flexible flatfoot (pes planus). It is also known as the “Hubscher maneuver.” The test is typically performed while the patient is standing. The examiner dorsiflexes the big toe (hallux) while observing changes in the arch of the foot. A positive result is indicated by the formation of an arch when the big toe is dorsiflexed, suggesting that the flatfoot is flexible and not rigid.

This test is based on the windlass mechanism of the foot. Dorsiflexion of the big toe tightens the plantar fascia, pulling the heel and the ball of the foot closer together and raising the arch. In a patient with a functional (flexible) flatfoot, this mechanism remains intact, and the arch reappears when the toe is lifted. However, in cases of rigid flatfoot, the arch remains flat despite dorsiflexion of the toe, indicating a more serious structural problem that may require orthopedic intervention.

Jack’s test is a simple yet valuable tool for distinguishing between flexible and rigid flatfoot, helping clinicians guide treatment strategies. Flexible flatfoot is often managed conservatively with physical therapy, orthotics, or footwear modification, while rigid flatfoot may necessitate more invasive interventions. Jack’s test can also be useful in pediatric assessments, as flatfoot is common in children and often resolves with age. By providing insight into foot mechanics, the test aids in early detection and proper management of arch-related foot disorders.

Most Useful Resources:
Jacks Test (Podiapaedia)
Jacks Test and failure of STJ supination with ext tibia rotation (Podiatry Arena)
Is Jacks test valid? (Podiatry Arena)
The Hubscher maneuver or Jacks test? (Podiatry Ninja)
Jacks Test (Bunion Surgery)