Defining varus thrust assessment and measurement: A scoping review

The primary aim of this scoping review was to identify and evaluate the methodologies used for classifying and quantifying varus thrust of the knee during walking. The secondary aim was to report outcomes of reliability, validity, prevalence, and quantitative cutoffs of varus thrust in existing studies.

A systematic literature search was conducted across five electronic databases from inception to April 2024. Studies that reported varus thrust during gait in adults were included. Two independent reviewers extracted data, and data were synthesized based on thrust classification methods, prevalence, reliability, and validity results.

A total of 59 studies were included. Varus thrust was classified by observational methods (k = 22) with three different definitions used, three-dimensional motion capture systems (k = 20), and wearable three-dimensional motion sensors (k = 17). Reliability of both classification and quantification of varus thrust were reported by 27% of studies, with kappa values ranging from moderate to high (0.46-0.92). Only three studies reported diagnostic validity of their quantification methodology and their corresponding prevalence. 30 studies reported prevalence of varus thrust, however five different definitions were used across these studies, yielding prevalence values that ranged from 16% to 81.8%, with higher rates reported by three-dimensional motion sensor-based studies.

In conclusion, this scoping review identified various methodologies for classifying and quantifying varus thrust, including observational methods and quantitative techniques. Reliability and validity assessments were reported inconsistently, as most studies did not report reliability and validity results. Prevalence of varus thrust ranged widely depending on the methodology used.