Increased knee flexion and varus moments during gait with high-heeled shoes: A systematic review and meta-analysis

Background: High-heeled shoes have been thought to alter lower extremity joint mechanics during gait, however its effects on the knee remain unclear. Research question: This systematic review and meta-analysis aimed to determine the effects of high-heeled shoes on the sagittal- and frontal-plane knee kinetics/kinematics during gait. Methods: 1449 studies from 6 databases were screened for the following criteria: 1) healthy adult females, 2) knee joint kinematics/kinetics reported for the early stance phase during gait under varying shoe heel heights (including barefoot). Excluded studies included those mixing different shoe styles in addition to altering the heel heights. A total of 14 studies (203 subjects) met the selection criteria, resulting in 51 and 21 Cohen?s d effect sizes (ESs) comparing the differences in knee sagittal- (flexion) and frontal-plane (varus) moment/angle, respectively, between shoes with higher heels and shoes with lower heels/barefoot. Results: Meta-analyses yielded a significant medium-to-large effect of higher heels compared to lower heels on increasing knee flexion moment (overall ES = 0.83; P < 0.01), flexion angle (overall ES=0.46; P < 0.01), and varus moment (overall ES=0.52; P < 0.01) during the early stance phase of gait. The results of meta-regressions used to explore factors explaining the heterogeneity among study ESs revealed that a greater ES in the knee flexion moment was associated with an elevated heel height of the high-heeled shoes (P = 0.02) and greater body mass of the individuals (P = 0.012). A greater ES in the knee varus moment during high-heeled gait was associated with a greater body height (P = 0.003) and mass (P = 0.006). Significance: Given the association between increased knee flexion/varus moments and risk of developing knee osteoarthritis (OA), women who wear high-heel shoes frequently and for a long period may be more susceptible to knee OA. Preventive treatments, such as lower extremity muscle strengthening, may help improve shock absorption to decrease knee loading in high-heel users.