Increased medial anterior tibial translation and reduced tibiofemoral rotation are observed during weight bearing in anterior cruciate ligament‐deficient knees: A paired within‐subject imaging analysis

Purpose: To evaluate the effect of weight-bearing computed tomography (WBCT) on knee kinematics in anterior cruciate ligament (ACL)-deficient knees using a within-subject comparison between WBCT and non–weight-bearing conditions (NWBCT). Methods: This was a prospective within-subject observational imaging study. Patients with chronic ACL deficiency underwent both WBCT and NWBCT cone-beam computed tomography scans of the same knee. Femorotibial rotation (FTR), medial and lateral anterior tibial translation (ATT), and trochlear groove–patellar tendon angle (FTR 2-PTTG) were measured using standardised multiplanar reconstructions. Interobserver reliability was assessed using intraclass correlation coefficients (ICC), while paired t-tests were used to compare measurements between WBCT and NWBCT conditions. Results: A total of 16 patients (mean age 35.6 ± 10.2 years) were included. WBCT conditions resulted in a significant reduction in FTR compared to NWBCT (3.83 ± 3.30 vs. 8.50 ± 5.10 degrees; p = 0.011) and a significant increase in medial ATT (5.52 ± 3.30 vs. 2.83 ± 3.68 mm; p = 0.021). No significant differences were observed for lateral ATT or FTR 2-PTTG. Interobserver reliability was good to excellent for most measurements (ICC range 0.87–0.98), whereas FTR 2-PTTG demonstrated moderate interobserver reliability (ICC range 0.59–0.71). Correlation analysis revealed a strong positive association between FTR and lateral ATT under NWBCT conditions (r = 0.85, p < 0.001). Conclusions: WBCT significantly alters knee kinematics in ACL-deficient knees, resulting in increased medial ATT and reduced FTR compared with NWBCT conditions. These findings suggest that conventional imaging may not fully reflect knee kinematics under physiological loading conditions. Level of Evidence: Level II, prospective within-subject observational imaging study.