An Achilles tendon injury can be devastating. Surgical methods to bring the muscle to full strength are not always available. Proposed is an ankle foot orthosis (AFO) that is entirely passive (does not add energy to the system) and uses the mechanical advantages provided by the walking gait of a person to decrease the energy exerted by the Achilles tendon during locomotion. The device is an exoskeleton consisting of two eccentric cams located near the knee joint that connect to extension springs. A lever arm extending horizontally from the ankle loads and unloads the springs through a lightweight twine. The main advantages of this AFO can be seen in cost, manufacturability, and adaptability. The AFO will be constructed from off-the-shelf parts purchasable through worldwide distributors and from rigid plastic components fabricated through additive manufacturing processes. This allows for a low cost, easily constructible exoskeleton that can be “printed” in any location. Furthermore, the spring/cam system mimics the advantages found in compound bows. The spring is extended during the locomotion phase where gravity and forward momentum are the driving loading forces. The result is a system that provides force in parallel with the Achilles tendon when its force exertion is at a maximum. All parameters of the device can be adjusted to fit any sized person and any severity Achilles injury. This Achilles assistance device bridges the gap between expensive conservative solutions and lengthy rehabilitation processes for Achilles tendon injuries
