01/02/2023
Treatment of Medial Compartment Knee Osteoarthritis with Valgus-Wedged Insoles and Orthoses
I have been using valgus-wedged insoles and orthoses in the treatment of mild to moderate medial knee osteoarthritis (OA) with good results for over three decades. Valgus-wedged insoles/orthoses act to effectively reduce the pain of medial knee OA by shifting ground reaction force (GRF) more laterally on the plantar foot during weightbearing activities. In turn, this lateral shift in GRF decreases the external knee adduction moment and lessens the magnitude of compression force acting within the medial knee compartment (see illustration below from: Hinman RS, Bowles KA, Metcalf BB, Wrigley TV, Bennell KL. Lateral wedge insoles for medial knee osteoarthritis: effects on lower limb frontal plane biomechanics. Clinical biomechanics. 2012 Jan 1;27(1):27-33).
In a foot standing on a flat shoe insole (on left of my illustration), the location of the center of pressure (CoP) will be located in a more central position on the plantar forefoot. With the simple addition of two layers of 1/8" (3 mm) adhesive felt (or other similar material) from the rearfoot to the forefoot to form a full-length valgus wedge within the insole of the shoe of a patient with medial knee OA, a temporary valgus rearfoot-midfoot-forefoot wedge may be created to test the mechanical effects of valgus wedging on the pain of the patient with medial knee OA during walking gait (at center of my illustration).
Once the valgus-wedged insole is placed inside the shoe of the patient with medial knee OA, the GRF, and the CoP, are shifted more laterally on the plantar foot relative to the flat-insole condition with no valgus wedge (on right of my illustration). This lateral shift in CoP acting on the plantar foot, in turn, reduces the magnitude of external knee adduction moment and the internal compression forces between the medial femoral condyle and medial tibia within the knee.
Simple in-office shoe modifications such as the valgus-wedged insole described above are very useful clinical tools for determining whether valgus wedging will help reduce medial knee pain during walking in patients with medial knee OA. In addition, temporary valgus-wedged insoles are very helpful in determining the optimal amount of valgus wedging that may be required in a more permanent custom valgus-wedged foot orthosis with a lateral heel skive that can provide a more durable in-shoe treatment solution for patients who suffer from the pain of mild to moderate medial knee OA during weightbearing activities.
