Independent Testing of Wedges Effect on Medial Joint Peak Forces
Independent testing shows that these cushioned wedged insoles are effective in reducing the forces across the medial and or lateral compartments of the knee joint. Results have varied from subject to subject, day to day, the suppleness of the foot and ankle, and with the variety of shoe types.
The following bar graphs support our clinical experience concerning the rationale for use of these insoles in degenerative arthritis of the knee, one compartment or the other. They also would be helpful for patients that have recently undergone surgery on one knee compartment or the other, especially cartilage repair work.
The testing performed with the subject walking barefoot showed the cushioned wedged insoles to reduce the forces on the intended compartment. The subject walked in stocking feet and insoles were placed inside the stocking. When placed elevated lateral, the medial joint force is reduced. When elevated to the inner side of the shoe, the forces show increased medial force in this chart which means the inverse is so; the lateral compartment forces are reduced as intended.
This bar graph shows the results of testing in one subject. The yellow bar is the control walking bar foot in stocking feet. The laterally placed elevated cushioned wedged insoles of 2.5 and 5.0 degree slopes decreased the medial joint forces in the knee. Those placed elevated on the lateral side of the shoe had a positive effect in increasing the load medially in this bar graph which means the lateral load was inversely reduced. This happened in all but one, the 2.5 sloped barefoot tests.
Results of testing have varied from patient to patient and with various shoe types. The tests also show that a restricted subtalar (below the ankle) motion will dampen the effect of the cushioned wedged insoles. The reason appears to be that the foot and ankle must first respond to the altered force at foot impact to create a relative flat (plano valgus) foot position. It is known that people with this foot position tend to have a knocked knee which in effect reduces the forces across the medial joint. That result is exactly what is intended with the lateral elevation of the wedged insole placed laterally in the shoe. A patient with a normal foot and ankle position may notice initially the forces the wedged insoles produce with some mild temporary discomfort on the inner ankle ligament (Deltoid ligament).