Effect of medially posted orthoses on lower extremity biomechanics in walking and running
A number of researchers and clinicians have emphasized the importance of forefoot abnormalities, suggesting its potential for causing injuries to the lower extremity. Recent evidence indicates that individuals with a large forefoot varus(> 15°) had a greater amount of forefoot pronation than those with less forefoot varus. It has also been suggested that elderly individuals with a large forefoot varus were more likely to have hip osteoarthritis and the need for total hip replacement. However, rearfoot foot orthoses are more widely used for treating lower extremity running injuries. The purpose of this dissertation was to examine the kinematic and kinetic effects of medially posted orthoses that have full-length posting through the forefoot extended to the big toe in addition to a small posting on the rearfoot during (1) walking and (2) running. Fifteen participants volunteered for these two studies. In the first study, kinematic and kinetic variables during overground walking were compared with the participants wearing sandals or sandals with orthoses. Orthoses increased ankle inversion moment, knee varus moment during late stance, and knee varus impulse; and reduced medio-lateral ground reaction force, adduction free moment, forefoot eversion angle, ankle eversion moment, hip adduction angle and moment, and hip internal rotation moment and impulse (p < 0.05). In the second study, kinematic and kinetic variables were compared during overground running with the participants wearing sandals or sandals with orthoses. Orthoses increased ankle inversion moment and knee varus moment and impulse; and reduced adduction free moment, forefoot eversion angle and timing, ankle eversion moment, knee internal rotation moment and impulse, and hip internal rotation moment and impulse (p < 0.05). The results of this research indicate that forefoot and rearfoot posted orthoses are effective in constraining forefoot eversion and reducing the torsional forces on the lower extremity. Orthoses are more effective on the frontal plane kinematics and kinetics in walking and on the transverse plane kinetics in running. These findings suggest the importance of addressing forefoot abnormalities in the design and manufacture of orthoses for treating individuals with chronic, non-traumatic injuries.
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