ACL reconstruction with lateral extra-articular tenodesis improves early quadriceps strength and thickness during the first 9 months, predominantly in the vastus intermedius.

BACKGROUND: Quadriceps weakness and atrophy are most pronounced within the first three months following anterior cruciate ligament reconstruction (ACLr). Whether the addition of lateral extra-articular tenodesis (LET) accelerates recovery of quadriceps thickness, strength, and function remains unclear. Therefore, we aimed to describe the time course of recovery in quadriceps strength, muscle thickness, and International Knee Documentation Committee (IKDC) scores between 3 and 9 months following ACLr, with and without LET. METHODS: A total of 268 patients with ACLr (201 men; 115 with LET; mean age 30.4 ± 10.5 years, weight 77.8 ± 14.6 kg, height 1.72 ± 0.08 m) were included from 2019 to 2025. Quadriceps thickness, strength, and IKDC score were assessed at 3, 6, and 9 months postoperatively. Latent growth modeling (intercept and slope) was performed to evaluate adaptations over time between groups (with and without LET) from 3 to 9 months (α = 0.05). RESULTS: Outcomes improved over time (per 3-month interval) in both groups (with and without LET). IKDC scores increased by 13.4 and 13.9 points, respectively (both p < 0.001). Quadriceps strength increased by 11.2 N in the LET group (p < 0.001) and 5.9 N in the non-LET group (p = 0.155). Total quadriceps thickness increased by 0.71 and 0.63 cm, respectively (both p < 0.001). Similar increases were observed for rectus femoris (0.17 vs 0.14 cm), vastus intermedius (0.20 vs 0.13 cm), and vastus medialis thickness (0.17 vs 0.13 cm), all p < 0.001. CONCLUSION: Quadriceps thickness and strength between 3 and 9 months following ACLr show greater improvement when combined with LET, whereas IKDC scores show similar recovery regardless of LET use. These findings suggest that adding LET to ACLr results in a faster restoration of quadriceps thickness and strength within the first nine postoperative months.