Study of How An Ankle Strap Changes Effects of Insole Treatment for Knee Osteoarthritis

Medial Compartment Knee Osteoarthritis

The goal of this project is to assess the effects of an ankle strap on the effectiveness of a laterally-wedged insole with ankle strapping in reducing knee symptoms and improving static and dynamic lower limb biomechanics. Using a repeated measures, modified cross-over design, the following aims and hypotheses will be addressed: Biomechanical Hypotheses 1. Use of the insole with ankle strapping significantly alters hip-knee-ankle (HKA) angle towards 180° or talar valgus angulation. 2. Use of the insole with ankle strapping significantly reduces peak knee external varus moment during gait. 3. Use of the insole with ankle strapping significantly reduces foot external rotation (out-toeing) or widened base during gait analysis. 4. The radiographic HKA angle and tilt angle of the talus will predict knee peak external varus moment during gait. Clinical Hypotheses 1\. The use of an insole with ankle strapping over a two-week period will reduce knee pain (Visual analogue scale, and Knee Osteoarthritis Outcome Survey).

Osteoarthritis (OA) of the knee is a common cause of pain and disability and the medial compartment is involved most frequently. If conservative mechanical therapies could reduce knee OA symptoms, risks to patients might be minimized through reduction in use of pharmacotherapy or surgery. A lateral heel wedge with strapping of the ankle joint has been reported to induce a similar therapeutic effect to that of proximal tibial osteotomy. It is presumed that the mechanism for this involves correction of genu varum. However, the effects on the static lower limb mechanical axis and the dynamic knee adduction moment, a risk factor for knee OA symptoms and progression, have not been assessed, so the mechanism of effect is currently unknown. The proposed protocol would compare lower limb mechanical alignment (measured by radiographic hip-knee-ankle angle) and dynamic knee varus moment (measured by 3-dimensional gait analysis) with and without the strapped insole to further understanding of the mechanism of effect on subjects with knee OA. Additionally, this protocol would assess analgesia and whether use of the insole reduces known knee joint unloading compensatory mechanisms during gait. Through measurement of radiographic lower limb alignment, dynamic knee varus moment, and ankle/foot static and dynamic angles, a model would be developed relating radiographs with dynamic moments, potentially allowing greater risk stratification for knee OA development and progression through use of radiographs. In addition to elucidating the mechanism of effect of this insole and developing a model for radiographic interpretation, this protocol would be the fist study of this insole involving non-Japanese subjects.

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