Effectiveness of a lateral-wedge insole on knee varus torque in patients with knee osteoarthritis

Abstract Kerrigan DC, Lelas JL, Goggins J, Merriman GJ, Kaplan RJ, Felson DT. Effectiveness of a lateral-wedge insole on knee varus torque in patients with knee osteoarthritis. Arch Phys Med Rehabil 2002;83:889-93. Objectives: To test whether a lateral-wedged insole, inclined at 5° or 10°, significantly reduces knee varus torque during walking in patients with knee osteoarthritis compared with both using no insole and with wearing nonwedged control insoles of the same material and average thickness. Design: Patients with medial knee osteoarthritis were studied while they walked wearing their comfortable shoes (1) without an insole; (2) with a 5° lateral wedge compared with a nonwedged, 3.175-mm (1/8-in) even-thickness control insole; and (3) with a 10° lateral wedge compared with a nonwedged 6.35-mm (¼-in) even-thickness control insole. Setting: A gait laboratory with 3-dimensional motion analysis and force platform equipment. Participants: Fifteen patients with clinical and radiographic osteoarthritis of the medial compartment of 1 knee. Interventions: Not applicable. Main Outcome Measures: Peak external knee varus torques during the stance period of gait. Data regarding lower-extremity joint torques and motions were collected, and knee joint torques using the different insoles and wedges were compared by analysis of variance. Results: Although responses varied among individuals, as a group, both the 5° and 10° lateral-wedge insoles significantly reduced the knee varus torque during walking compared with walking with no insole and walking with nonwedged 3.175-mm and 6.35-mm control insoles. Compared with no insole, the 5° wedge reduced the peak knee varus torque values by about 6% and the 10° wedge reduced the peaks by about 8%. Although there were no significant differences in speed of walking between the conditions, the 10° wedge and 6.35-mm control insoles were associated with varying degrees of discomfort. Conclusion: Both wedge insoles are effective in reducing the varus torque during walking beyond what theoretically could be explained by a reduced walking speed or cushioning effect from the insole. These data imply that wedged insoles are biomechanically effective and should reduce loading of the medial compartment in persons with medial knee osteoarthritis. Although the effect of the 5° wedge was smaller, it may be more comfortable than the 10° wedge to wear inside one's own shoes. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation