A link extends between a distal member and a proximal member of a wearable device, such as an exoskeleton, orthosis or prosthesis for a human lower limb. One or other of the distal member and the proximal member includes a crossing member. The link extends from the crossing member of the distal member or the proximal member, to the other of the distal member or the proximal member. Actuation of the link translates to a force at the distal or proximal member that is normal to a major longitudinal axis extending through the distal and proximal members. In one embodiment, a sliding link of a device configured for use with a human joint tracks two degrees of freedom of the joint.