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

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.

Inclusion criteria

• Subjects aged 45 or over will be included if they have predominantly medial compartment knee OA by American College of Rheumatology criteria, with medial knee pain rated at least 40/100mm on a visual analogue scale on most days of the month during one of the past 3 months.

Exclusion criteria

• Potential subjects with a body mass index (BMI) of greater than 35 will be excluded to avoid the potential confounding effect of increased weight on the height of the insole. Other exclusion criteria will include: known injury or surgery involving bone or cartilage of the knee or ankle which may alter gait, history of factors which might alter response to use of a laterally wedged insole (e.g. greater or similar reduction in lateral compared with medial femorotibial jont space width on posterior-anterior radiographs, tibial osteotomy, congenital foot problems, fused joints, foot deformity, known limitation of range of motion of the subtalar joint), known neuromuscular disease, co-morbid disease which might confound gait analysis (e.g. hip OA, ankle OA, hallux rigidus, valgus deformity of the midfoot, other symptomatic deformity of the foot, advanced arthroplasty of the hindfoot, previous ankle arthrodesis, unable to walk without a gait aid), current use of an orthotic insole, inability to comply with study protocol.