The effect of wedged insoles on the thrust of osteoarthritic knees

We describe a method of quantifying the lateral/medial thrust of the knee which occurs in the early phase of walking. We have used this method to evaluate the effects of wedged insoles on the lateral and medial thrust for normal knees and knees with unicompartment osteoarthritis (OA). A laterally elevated (valgus) insole decreased the lateral thrust of both normal and osteoarthritic knees. A medially elevated (varus) insole increased the lateral thrust. In 50 symptomatic knees with medial compartment OA, decreasing the lateral thrust with a valgus insole reduced pain on walking in 27. Patients whose pain was reduced by valgus insoles tended to have earlier OA and to have a significantly greater reduction in the lateral thrust than in the 23 remaining unaffected knees. A varus insole was effective in decreasing the medial thrust and reducing pain in all ten knees with lateral compartment OA. We recommend the use of valgus insoles for patients with painful early medial compartment OA and the use of varus insoles for lateral compartment OA.