Knee Adduction Moment and Medial Contact Force – Facts about Their Correlation during Gait

Abstract

The external knee adduction moment is considered a surrogate measure for the medial tibiofemoral contact force and is commonly used to quantify the load reducing effect of orthopedic interventions. However, only limited and controversial data exist about the correlation between adduction moment and medial force. The objective of this study was to examine whether the adduction moment is indeed a strong predictor for the medial force by determining their correlation during gait. Instrumented knee implants with telemetric data transmission were used to measure tibiofemoral contact forces in nine subjects. Gait analyses were performed simultaneously to the joint load measurements. Skeletal kinematics, as well as the ground reaction forces and inertial parameters, were used as inputs in an inverse dynamics approach to calculate the external knee adduction moment. Linear regression analysis was used to analyze the correlation between adduction moment and medial force for the whole stance phase and separately for the early and late stance phase. Whereas only moderate correlations between adduction moment and medial force were observed throughout the whole stance phase (R2 = 0.56) and during the late stance phase (R2 = 0.51), a high correlation was observed at the early stance phase (R2 = 0.76). Furthermore, the adduction moment was highly correlated to the medial force ratio throughout the whole stance phase (R2 = 0.75). These results suggest that the adduction moment is a surrogate measure, well-suited to predicting the medial force ratio throughout the whole stance phase or medial force during the early stance phase. However, particularly during the late stance phase, moderate correlations and high inter-individual variations revealed that the predictive value of the adduction moment is limited. Further analyses are necessary to examine whether a combination of other kinematic, kinetic or neuromuscular factors may lead to a more reliable prediction of the force magnitude.

Biomechanical Analysis of the Knee Joint Load During a Unilateral Sit-to-Stand Movement

“…We suspect this to be due to an increased lateral evasive movement of the knee during the unilateral STS movement from the low chair height leading to a more medial course of the ground reaction force vector. These findings might be important when executing STS movements with subjects suffering from medial compartment knee osteoarthrosis, as increased knee adduction moments have been associated with increased medial compartment knee joint load [42]. The increasing anterior shear forces observed with decreasing chair height might be explained by a greater contraction of the quadriceps muscle.…”

Biofeedback for Gait Retraining Based on Real-Time Estimation of Tibiofemoral Joint Contact Forces

“…3). However, variability in MTFF across subjects has been shown using instrumented knee implants [39], so it is not surprising to observe such variability in healthy individuals as well.…”

“…The KAM has been positively correlated with the shape of MTFF during walking [7, 39], but this is not always the case [3, 4, 37, 40]. Studies based on instrumented tibiofemoral prostheses [41] have shown that decreases in the KAM do not necessarily result in decreases to MTFF [37], and that only small changes occurred in the MTFF for gait patterns designed 1to reduce KAM [42].…”

Are Instrumented Knee Forces Representative of a Larger Population of Cruciate-Retaining Total Knee Arthroplasties?

“…The study also identified strategies for proper tuning of this parameter which we used in this study [28]. Although previous investigations have found that the medial-lateral force ratio is correlated with the external knee adduction moment [23,29], it is uncertain as to whether this relationship holds true for all activities and whether it may be influenced by patient characteristics such as knee alignment [30,31]. Specifically, for chair sitting and rising the medial-lateral force ratio of 50%, indicating equal force transfer between the medial and lateral sides of the tibial plateau, was necessary to obtain forces with the computational model.…”