Calcaneal Eversion Affects Coupled Knee Rotation During Gait

Abstract

It has been suggested that ankle motion (specifically, subtalar (ST) and tibiotalar (TT) joints) may contribute to knee pathologies such as patellofemoral pain syndrome. Yet, in-depth understanding of knee and ankle joint coupling remains elusive due to challenges in accurately measuring three dimensional (3D) bone motion in vivo. PURPOSE: To determine coupled knee and ankle kinematics during the weight-bearing phase of gait in healthy adults. METHODS: Dynamic biplane radiography was used to measure coupled kinematics during walking in 12 ankles and knees from six healthy volunteers (ages 18 - 35 yrs.). Synchronized biplane radiographs were collected at 100hz over the entire support phase of gait, from foot-strike through toe-off. Next, CT scans were acquired and subject-specific models of each bone were generated and used to track the 3D bone motion during each trial using a validated technique with sub-millimeter and sub-degree accuracy. Six degrees of freedom ankle and knee kinematics were normalized to percent stance and divided into loading, mid-stance, and push-off phases. The coupled outcome kinematics were 1) ST inversion and knee internal rotation, and 2) TT dorsiflexion and knee flexion. Associations between ankle and knee coupled kinematics were evaluated using Spearman’s rho with significance set at p<0.05. RESULTS: During midstance, the knee internal rotation always accompanied ST inversion while external rotation accompanied eversion (R2=0.63, p=0.085) (Figure 1). During mid-stance TT plantar flexion always occurred with knee extension (R2=0.12, p=0.71). CONCLUSIONS: In healthy knees, ST inversion/eversion appears to play a role in knee internal rotation during the mid-stance of gait. This finding suggests assessing coupled motion between the knee and ankle may be beneficial for evaluating single joint pathology. This work was supported by NIH Grant: R44HD066831.Figure 1: Chart showing coupled ST inversion and knee external rotation during mid stance of gait.