Reliability and Clinical Utility of Anterior Tibial Subluxation on Weight-bearing Extended Lateral Knee Radiographs in Anterior Cruciate Ligament-deficient Knee.

Abstract

Anterior tibial subluxation (ATS) measured on weight-bearing extended lateral knee radiographs is being increasingly used to evaluate anterior cruciate ligament (ACL) injury. However, standardized measurement methods and their clinical relevance are yet to be established. This study aimed to evaluate the reliability and clinical utility of ATS measurements obtained from weight-bearing extended lateral knee radiographs for assessing knee instability in ACL-deficient knees. This retrospective multicenter ACL reconstruction cohort study included patients who underwent preoperative weight-bearing extended lateral knee radiography between August 2022 and July 2025. ATS was measured using articular surface-based (AS-ATS) and bone axis-based (BA-ATS) methods at the lateral and medial sides, with the midpoint (average of lateral and medial) and lateral-medial difference calculated. Intra- and inter-rater reliabilities were assessed using intraclass correlation coefficients. To examine the influence of the knee flexion angle on imaging, patients were stratified in 5° increments, with 0° to <5° as the reference. Welch's t-test was used to compare ATS values, and ranges showing statistically significant differences were considered inappropriate and excluded. Univariate analyses were used to compare ATS parameters between the high- and low-grade Lachman and pivot shift test groups, and parameters with statistically significant differences were further evaluated using multiple linear regression adjusted for demographic and injury-related covariates. A total of 266 patients (median age, 24 years; 122 male) were analyzed. The intra- and inter-rater reliabilities were good-to-excellent across all ATS parameters. Analyses restricted to radiographs obtained at <10° for AS-ATS and -5° to <10° for BA-ATS demonstrated that lateral BA-ATS and midpoint BA-ATS were statistically significantly different with the Lachman grade in both univariate (All P<0.001) and multivariate (P<0.001 and P=0.002, respectively) models. No ATS parameters demonstrated a statistically significant difference between the pivot shift grade. ATS measured on weight-bearing extended lateral knee radiographs demonstrated high reliability in ACL-deficient knees. Ensuring near-full extension at the time of imaging improves the validity of the ATS measurements. Lateral and midpoint ATS using bone axis methods were independently associated with the Lachman grade, supporting their role as relatively objective radiographic parameters reflecting anterior knee laxity. III.