Lateral Extra-articular Tenodesis Does Not Alter Early Gait Biomechanics After ACL Reconstruction in a Pediatric Population: A Motion Analysis Study

Background: Lateral extra-articular tenodesis (LET) is increasingly added to anterior cruciate ligament reconstruction (ACLR) to reduce graft failure and improve rotatory stability. However, concerns remain that LET may overconstrain the lateral compartment, alter gait biomechanics, and contribute to degenerative changes, especially in pediatric patients. Hypothesis/Purpose: The purpose of this study was to compare 3-dimensional (3D) knee kinematics during gait between pediatric patients who underwent ACLR with LET (ACLR+LET) and those who underwent isolated ACLR (iACLR). It was hypothesized that patients with ACLR+LET would show modified postoperative gait biomechanics compared to those with iACLR, namely decreased tibial internal rotation and increased valgus during the unloading phase. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective study included pediatric patients (≤18 years of age) who underwent ACLR with or without LET between January 2023 and January 2026. All participants underwent standardized gait assessment with knee kinesiography pre- and postoperatively. Primary outcomes were 3D knee kinematic waveforms in the sagittal, frontal, and transverse planes, analyzed using 1-dimensional statistical parametric mapping. Results: In total, 70 pediatric patients (70 knees; mean age 15.8 ± 1.3 years) were included: 35 in the iACLR group and 35 in the ACLR+LET group. Preoperatively, a small but statistically significant difference in tibial rotation (1.8°) was identified between 34% to 38% ( P = .032) and 57% to 59% ( P = .034) of the gait cycle. At approximately 4 months postoperatively (123.3 ± 58.4 days), no significant between-group differences in knee kinematics were detected in any plane of motion (all P > .05). The mean postoperative tibial rotation was 1.03°± 4.27° in the iACLR group versus 1.61°± 3.51° in the ACLR+LET group. Conclusion: In this pediatric cohort, adding LET to ACLR did not significantly alter early 3D gait biomechanics at approximately 4 months postoperatively. These findings support the safety of LET as an adjunct to ACLR in young patients. Longitudinal studies with higher-demand functional assessments are needed to confirm these results beyond the early postoperative period.