The Effect Of Foot Progression Angle On Knee Joint Loads During Gait

Abstract

The mechanical loads placed on the knee during gait, in particular the adduction moment (KAM), have been implicated in the progression of knee osteoarthritis (OA). Those presenting with symptomatic medial compartment knee OA tend to adopt a toe out gait pattern reducing the peak KAM during gait, hence unloading the diseased medial compartment. Although this is known, the relationship between the foot progression angle (FPA) and the KAM, along with other knee gait kinetic measures has yet to be determined. PURPOSE To determine the relationship between FPA and 3D knee gait forces and moments. METHODS Gait analysis was performed on 11 healthy subjects (23 +/− 1.7 yrs). Subjects performed five trials in each of three conditions: natural foot position (NFP), approximately 30 degrees internally rotated (IR) and approximately 30 degrees externally rotated (ER) from their natural position. 3D knee joint forces and moments were compared to true FPA (ANOVA) and a regression analysis determined the relationships between normalized (by NFP) values. RESULTS Late stance peak KAM and medial-lateral shear forces (MLF) were significantly different across conditions, (KAM: ER=0.125, NFP=0.267, IR=0.410 Nm/kg; p<0.01 and MLF: ER=−0.980, NFP=−1.248, IR=−1.447 N/kg; p<0.01). See Figure 1 for average gait curves. There were also strong relationships between changes in FPA (actual range of 49.3 ±) and changes in KAM (R2=.97) and MLF (R2=.88).FigureCONCLUSIONS Results suggest that for every 10 degree change in FPA there is a 21.7% change in KAM and a 7.6% change in MLF during late stance. This may have implications in preventing the development and progression of knee OA.