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Abnormal loading of the medial compartment of the knee is believed to be a contributing factor to the development of medial compartment knee osteoarthritis (OA) [1]. Treatment strategies for patients with medial knee OA include both invasive (i.e., surgery) and non-invasive (e.g., gait modification) options. A variety of modified gait patterns have been proposed as non-invasive treatments for patients with medial knee OA.

Medial compartment knee osteoarthritis is a common clinical disorder [1] in which the articular cartilage in the medial compartment progressively deteriorates. To slow disease progression without surgical intervention, researchers have proposed gait modifications to offload the medial compartment. Since knee medial contact force (MCF) cannot be measured non-invasively in vivo, researchers have identified the external knee adduction moment (KAM) as a surrogate measure that is easy to calculate [2]. A common assumption has been that reducing the peak KAM will result in a corresponding reduction in peak MCF. While the magnitude of the peak KAM has been correlated with disease severity and rate of disease progression [3,4], it is not clear that reduction of this external load via gait modification will always result in a decrease in internal MCF.Copyright © 2010 by ASME

Excessive contact force is believed to contribute to the development of medial compartment knee osteoarthritis. The external knee adduction moment (KAM) has been identified as a surrogate measure for medial contact force during gait, with an abnormally large peak value being linked to increased pain and rate of disease progression. This study used in vivo gait data collected from a subject with a force-measuring knee implant to assess whether KAM decreases accurately predict corresponding decreases in medial contact force. Changes in both quantities generated via gait modification were analyzed statistically relative to the subject's normal gait. The two gait modifications were a ''medial thrust'' gait involving knee medialization during stance phase and a ''walking pole'' gait involving use of bilateral walking poles. Reductions in the first (largest) peak of the KAM (32-33%) did not correspond to reductions in the first peak of the medial contact force. In contrast, reductions in the second peak and angular impulse of the KAM (15-47%) corresponded to reductions in the second peak and impulse of the medial contact force (12-42%). Calculated reductions in both KAM peaks were highly sensitive to rotation of the shank reference frame about the superior-inferior axis of the shank. Both peaks of medial contact force were best predicted by a combination of peak values of the external KAM and peak absolute values of the external knee flexion moment (R 2 ¼ 0.93). Future studies that evaluate the effectiveness of gait modifications for offloading the medial compartment of the knee should consider the combined effect of these two knee moments. 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1348-1354, 2010

Gait modification is a conservative, non-invasive treatment option for patients with medial compartment knee osteoarthritis. If proven effective for offloading the medial compartment, it may provide one of the few treatment options with disease modifying potential. Furthermore, it could fill an important therapeutic “hole” for patients in their 40’s and 50’s who no longer achieve sufficient pain relief through pharmacological means and yet are too young to receive a total knee replacement. A variety of gait modifications have been proposed for offloading the medial compartment, including toeing out [1], walking more slowly or with decreased stride length [2], walking with increased medial-lateral trunk sway [3], using lateral heel wedges [4], or walking with medialized knees [5]. These modifications have been proposed primarily based on their ability to reduce the external knee adduction torque. While this external measure is highly correlated with medial compartment contact force [6], the acid test is to demonstrate experimentally that a gait modification reduces medial contact force directly.Copyright © 2008 by ASME