Quadriceps Strength and Hamstring-to-Quadriceps Ratios in Pediatric Patients After ACL Reconstruction: Revisiting Norms from Adult Data

Sarthak Chopra; Geoffrey Murphy; Pradyumna Raval; Harbeer Ahedi; Alexander S Nicholls

doi:10.1177/23259671251360364

Quadriceps Strength and Hamstring-to-Quadriceps Ratios in Pediatric Patients After ACL Reconstruction: Revisiting Norms from Adult Data

Orthop J Sports Med. 2025 Aug 15;13(8):23259671251360364. doi: 10.1177/23259671251360364. eCollection 2025 Aug.

Authors

Sarthak Chopra¹, Geoffrey Murphy¹, Pradyumna Raval¹, Harbeer Ahedi¹, Alexander S Nicholls¹

Affiliation

¹ Sydney Orthopaedic Research Institute, Chatswood, New South Wales, Australia.

Abstract

Background: Pediatric patients who undergo anterior cruciate ligament reconstruction (ACLR) experience higher rates of graft failure and secondary knee injuries compared with adults. Neuromuscular recovery differences may contribute to these disparities.

Purpose/hypothesis: This study aimed to assess the effect of age on functional limb testing (FLT) outcomes at 9 months after ACLR. It was hypothesized that pediatric patients would demonstrate greater deficits compared with adults, which may help explain higher reinjury rates.

Study design: Cohort study; Level of evidence, 3.

Methods: All pediatric patients (≤16 years) who underwent hamstring autograft ACLR between 2017 and 2022 and completed FLT at 9 months after surgery were included. An adult cohort (>16 years) was matched for sex ratio, body mass index, meniscal pathology, preoperative Tegner activity score, and rate of double tendon graft constructs. FLT outcomes included quadriceps strength limb symmetry index (LSI), hamstring strength LSI, hamstring-to-quadriceps (H:Q) ratio, Y-balance test LSI, hop testing LSI, and ACL-Return to Sport after Injury (ACL-RSI) score.

Results: The final analysis included 120 pediatric and 210 adult patients. Pediatric patients demonstrated significantly higher quadriceps strength LSI (94% vs 88%; P < .001), hop distance LSI (97% vs 92%; P < .05), and hop height LSI (92% vs 84%; P < .001) compared with adults. However, adults exhibited a significantly higher H:Q ratio (48.90 vs 41.50; P < .001). No significant differences were observed in hamstring strength, LSI, or ACL-RSI scores.

Conclusion: At 9 months after ACLR, pediatric patients demonstrated a faster rate of recovery for quadriceps strength and hop function compared with adults. Both groups exhibited similar hamstring strength deficits. The lower H:Q ratio observed in pediatric patients may indicate a higher risk of reinjury, highlighting the need for targeted rehabilitation strategies to address hamstring deficits in this population.

Keywords: anterior cruciate ligament reconstruction; functional limb testing; hamstring strength; hamstring-to-quadriceps ratio; limb symmetry index; quadriceps strength; return to sports.