Tension is necessary to maintain and restore the mechanical properties of soft connective tissues. Conversely, reduced tension states such as produced by immobilization weaken mechanical properties and facilitate joint contracture. We assessed the effect of low torque-long duration stretching to increase the range of motion (ROM) and to restore the mechanical properties of contracted joints in 66 rat knees immobilized for 40 days. After remobilization, we randomly divided the contracted knees into four treatment groups treated with repeated stretches of diverse torques and duration: stretching with low-torque and long-duration, high-torque and short-duration, high-torque and long-duration, low-torque and short duration. We included control and natural recovery groups. Phase lag in all treatment groups recovered to the same range as in the normal controls. Dynamic stiffness, which was not altered by joint immobilization, increased in all treatment groups. Deformation and load to failure improved substantially only in the low-torque and long-duration stretching group. Low-torque and long-duration repeated stretching leads to a greater restoration of ROM with more normal mechanical properties compared to high-torque and short duration stretching.

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We have been developing a passive motion exercise device for ankle dorsiflexion/plantarflexion that can be applied to patients with complicated ankle joint deformity. In conventional ankle motion exercise devices, a footplate remains parallel to the axis of ankle dorsiflexion/plantarflexion. This may cause pain by forcing the ankle position to fit in the device and may also cause uneven contact of the sole to the footplate during the exercise. Therefore, we proposed to make a device which enables passive dorsiflexion/plantarflexion movements of ankle with adjustable inversion/eversion. In this study, the effect of passive joint of inversion/eversion is examined using pressure distribution on the footplate.

We propose here a new type of leg rehabilitation system. The aim of the system is to realize multiple-degree-offreedom (DOF) training of a leg by manipulating the patient S leg by wires. A single-DOF experimental system was built and tested, and the experimental results showed the feasibility of a wire-driven leg rehabilitation system. Next, a 2-DOF experimental system was designed, with a target motion of flexiodextension of both the hip and knee joints. Experiments of single-DOF motion on a test dummy and a male subject showed that the system generates enough accurate motion to support range of motion exercise. In addition, the results showed that the wire-driven mechanism would be a human-friendly system.