In one aspect, an ankle foot orthosis generally comprises a leg member, a foot member, and a drive assembly. The leg member is configured to be releasably fastened to a leg of the wearer. The foot member is configured to be releasably fastened to a foot of a wearer, the foot member having anterior and posterior ends. The drive assembly includes a link member hingedly secured to the foot member at a hinge location adjacent to the posterior end of the foot member.