E-Journal

  Effect of Cushioned Insoles on Knee Kinematics                                                      Issue No. 41

 

Several studies have shown that changes in shoes and orthoses can alter knee joint torques and affect pain caused by medial knee osteoarthritis (OA). We will review a study by Franz et al. that examined the effect of a common arch support cushion on knee varus torque.

 

Sincerely,
 
Cherri Choate, DPM
Larry Huppin, DPM
Alona Kashanian, DPM
Paul R. Scherer, DPM

 

The Influence of Arch Supports on Knee Torques Relevant to Knee Osteoarthritis
The purpose of this study was to determine if commonly used arch support cushions promote a medial force bias during gait similar to medial-wedged orthoses, thereby increasing knee varus torque during both walking and running.

 

Methods

        22 healthy runners with no history of running-related injuries

        Subjects walked and ran under two conditions using standardized footwear (New Balance 755 - neutral shoe, single-density midsole, semi-curved last):

o       No arch supports

o       With arch supports (Spenco full-length arch support cushion)

        16 anatomic markers and 10-camera motion analysis captured motion data

        Knee joint torque data in the sagittal, coronal and transverse planes was calculated

        Peak knee varus torque in early and late stance were measured which reflect the compressive force on the medial tibiofemoral aspect of the knee

Results

        Peak knee varus torque was significantly greater during running and in late stance during walking when arch support cushions were used

        Peak internal rotation torque during running was significantly greater with arch support cushions

 
Significance of the Article

The addition of arch support cushions significantly increased knee varus torque during both walking and running. In reviewing the results of this study, the authors state that "arch support cushions exaggerate compressive loading on the medial tibiofemoral compartment...[and] the amount of change observed in this study is likely to be clinically significant".

Significance for Orthotic Therapy

This study confirms that varus wedging has the ability to increase varus torque in the knee. This type of wedge can be found in custom orthoses, prefabricated cushioned insoles, or even as part of the shoe design. Since varus torque has been demonstrated to contribute to OA of the medial knee, the practitioner should understand how to modify orthoses to reduce torque on the medial knee. Many foot pathologies treated with orthotic devices respond very positively to varus wedging. However, when treating patients with medial knee OA, practitioners should weigh the advantages and disadvantages, and inform the patients of the potential deleterious effects of the varus wedge correction on the knee.

References