Quadriceps and Hamstring Strength Recovery Following Different Anterior cruciate ligament (ACL) Reconstruction Techniques: A Scoping Review of Graft Choices and Rehabilitation Protocols

Abstract

Background: Although there has been extensive research on anterior cruciate ligament reconstruction (ACLR) outcomes, a comprehensive synthesis of strength recovery and functional performance across different graft choices and rehabilitation protocols is still lacking. Objective: To systematically analyze quadriceps and hamstring strength recovery and functional performance outcomes following different ACLR graft choices (hamstring tendon [HT], quadriceps tendon [QT], bone-patellar tendon-bone [BPTB], anterior tibialis tendon [ATT]) and rehabilitation protocols. Methods: Following PRISMA-ScR guidelines, systematic searches were conducted across MEDLINE, Embase, Web of Science, SPORTDiscus, and Cochrane databases (January 2017-December 2024). Twenty-eight studies met inclusion criteria, examining strength outcomes in adult patients after primary ACLR using HT, QT, BPTB, or ATT grafts. Results: Our review revealed that isokinetic dynamometry was the primary assessment method in 82.14% of studies, with testing most frequently performed at 60°/s (46.15%), 180°/s (21.15%), and 240°/s (17.31%). HT autografts were most commonly utilized (47.92%), followed by QT (14.58%), BPTB (12.50%), and ATT (4.17%). At seven months post-ACLR, no surgical group achieved the clinical benchmark of 90% limb symmetry index (LSI) for quadriceps strength. HT recipients demonstrated greater hamstring deficits, while QT and BPTB recipients showed more pronounced quadriceps weakness. Combined eccentric-plyometric training produced superior strength gains compared to either modality alone during early rehabilitation (p<0.05). Single-leg hop testing revealed comparable performance between HT and QT recipients, though both groups showed significant deficits versus controls (p<0.01). Conclusion: Different ACLR graft choices demonstrate distinct strength recovery patterns. Combined rehabilitation protocols incorporating progressive strength training and neuromuscular exercises optimize outcomes. Return-to-sport decisions should consider multiple objective criteria including strength symmetry (LSI>90%) and functional performance rather than time alone. Future research should establish comprehensive, evidence-based return-to-sport testing protocols for minimizing reinjury risk.