# The Estimation of Knee Medial Force with Substitution Parameters during Walking and Turning

## TL;DR

This study examines how well certain knee parameters predict medial knee force during walking and turning, finding that knee adduction moment is the best predictor across different movements.

## Contribution

The study provides new evidence on the effectiveness of knee adduction moment as a surrogate for medial knee force during various walking and turning tasks.

## Key findings

- Peak knee adduction moment significantly predicts peak knee medial force during straight walking, step turning, and crossover turning.
- Peak knee flexion moment only predicts peak knee medial force during straight walking.
- Knee parameters during straight walking and step turning are more similar compared to crossover turning.

## Abstract

Purpose: Knee adduction, flexion moment, and adduction angle are often used as surrogate parameters of knee medial force. To verify whether these parameters are suitable as surrogates under different walking states, we investigated the correlation between knee medial loading with the surrogates during walking and turning. Methods: Sixteen healthy subjects were recruited to complete straight walk (SW), step turn (ST), and crossover turn (CT). Knee joint moments were obtained using inverse dynamics, and knee medial force was computed using a previously validated musculoskeletal model, Freebody. Linear regression was used to predict the peak of knee medial force with the peaks of the surrogate parameters and walking speed. Results: There was no significant difference in walking speed among these three tasks. The peak knee adduction moment (pKAM) was a significant predictor of the peak knee medial force (pKMF) for SW, ST, and CT (p < 0.001), while the peak knee flexion moment (pKFM) was only a significant predictor of the pKMF for SW (p = 0.034). The statistical analysis showed that the pKMF increased, while the pKFM and the peak knee adduction angle (pKAA) decreased significantly during CT compared to those of SW and ST (p < 0.001). The correlation analysis indicated that the knee parameters during SW and ST were quite similar. Conclusions: This study investigated the relationship between knee medial force and some surrogate parameters during walking and turning. KAM was still the best surrogate parameter for SW, ST, and CT. It is necessary to consider the type of movement when comparing the surrogate predictors of knee medial force, as the prediction equations differ significantly among movement types.