Restraining forces in various designs of knee ankle orthoses: their placement and effect on the anatomical knee joint

A biochemical evaluation was conducted on double upright knee ankle orthoses, which were instrumented with strain gauge transducers to determine the magnitudes of the restraining forces exerted on the leg. Measurements were made on six commonly used designs of orthoses worn by spinal cord injured persons ambulating with a swing-through gait. The measurements were used to determine distribution of forces on the limb as well as their effect on anatomical knee shear. Based on the experimental data, the following basic principles of optimal orthosis design were identified: The forces required to stabilize the knee should be minimized by applying the stabilizing force as close as possible to the knee center, and by maintaining the anatomical knee as straight as possible. When the major portion of the knee stabilizing force is applied below the knee, the shear on the anatomical knee structures is markedly reduced. Further, the stabilizing forces should be well distributed over tolerant areas.