Quadriceps and hamstring muscles strength differences in adolescent and adult recreational athletes 6 months after autograft bone-patellar-tendon-bone anterior cruciate ligament reconstruction: A retrospective study

Background: Knee muscle strength recovery after anterior cruciate ligament reconstruction (ACLR) is crucial for a safe return to sport (RTS) but it is poorly described in the adolescent population. Therefore, we compared the knee muscle strength at 6 months post-surgery in adults and adolescents. We hypothesized a greater muscular strength in adolescents 6 months after ACLR. Methods: This was a retrospective analysis of 55 adolescents (13-18 years old) and 76 adults (19-39 years old) who underwent ACLR with autograft bone-patellar-tendon-bone (BPTB), subjected to isokinetic tests 6 months after surgery. The following outcomes were analyzed: (1) the maximum torque of hamstrings (H) and quadriceps (Q) during flexion and extension at 30 degrees/s normalized by body weight; (2) hamstrings to quadriceps strength ratio (HQratio); (3) injured to uninjured leg muscle strength ratio (limb-symmetry index, LSI). Results: Both adults and adolescents produced lower Q torque with the injured leg compared with uninjured, but similar H torque. In adolescents, the injured Q torque and the Q-LSI were higher compared with adults. In both populations, the Q-LSI was lower than the H-LSI and the HQratio in the injured leg was higher compared with uninjured. Adolescents showed a lower HQ ratio in injured legs. Conclusions: At 6 months after ACLR both adolescents and adults did not recover Q strength in the injured leg. However, adolescents showed larger Q strength compared with adults. The HQratio analysis showed that 6 months after surgery both groups are not ready fora safe RTS. (c) 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).