8/22/13: It was reported yesterday that a review of the literature by meta analysis concluded that lateral wedged insoles have only a potential placebo effect for patients with medial compartment osteoarthritis of the knee.
Parkes MJ, Maricar N, Lunt M, LaValley MP, Jones RK, Segal NA, Takahashi-Narita K, Felson DT. Lateral Wedge Insoles as a Conservative Treatment for Pain in Patients With Medial Knee Osteoarthritis; A Meta-analysis. JAMA. 2013;310(7):722-730. doi:10.1001/jama.2013.243229.
Counter Point: The necessary factor for shifting of axial loads away from the meidal compartment of the knee were not present in the studies. The essential inclusion criteria for effective use includes the patient having a compliant subtalar motion plus compliant passive laxity of the medial knee joint capsule and ligamentous structures. See www.drlannysinsoles.com for illustrations of such testing.
If the foot and ankle cannot be passively moved into eversion (turned out) position then there would be no angulation force transmitted up the leg to the knee by the use of a lateral wedged insole. If the inner structures of the knee are tight and not compliant to allow the the transmitted axial force up the leg to open the medial aspect of the knee, there would be no physical change to the force on the medial compartment of the knee.
The medical literature supports the effectiveness of a reduction in force across an arthritic joint to result in architectural structural changes in the bone next to the joint and grow cartilage on a joint surface. Look at www.golfersknee.com/MedicalLiterature
Another factor for success of wedged insoles is the nature of the material to maintain its integrity to transmit the force without significant deformation of the material.