Minimum detectable change for knee joint contact force estimates using an EMG-driven model

Abstract

Adequate test–retest reliability of model estimates is a necessary precursor to examining treatment effects or longitudinal changes in individuals. PurposeThe purpose of this study was to establish thresholds for minimal detectable change (MDC) for joint contact forces obtained using a patient specific EMG-driven musculoskeletal model of the knee. DesignA sample of young, active individuals was selected for this study, and subjects were tested on 2 separate days. Three-dimensional motion analysis with electromyography (EMG) was used to obtain data from each subject during gait for model input. An EMG-driven modeling approach was used to estimate joint contact forces at each session. ResultsMDC's for contact force variables ranged from 0.30 to 0.66BW. The lowest MDC was for peak medial compartment force (0.30BW) and the highest was for peak tibiofemoral contact force (0.66 BW). Test–retest reliability coefficients were also reported for comparison with previous work. ConclusionsUsing the present model, changes in joint contact forces between baseline and subsequent measurements that are greater than these MDCs are greater than typical day-to-day variation and can be identified as real change.