title: Influence of Anterior Cruciate Ligament Tear on Thigh Muscle Strength and Hamstring-to-Quadriceps Ratio: A Meta-Analysis.
abstract: Theoretical compensation after anterior cruciate ligament (ACL) tear could cause quadriceps weakness and hamstring activation, preventing anterior tibial subluxation and affecting the expected hamstring-to-quadriceps ratio. Although quadriceps weakness often occurs after ACL tears, it remains unclear whether hamstring strength and hamstring-to-quadriceps ratio increase in ACL deficient knees. This meta-analysis compared the isokinetic muscle strength of quadriceps and hamstring muscles, and the hamstring-to-quadriceps ratio, of the injured and injured limbs of patients with ACL tears. This meta-analysis included all studies comparing isokinetic thigh muscle strengths and hamstring-to-quadriceps ratio in the injured and uninjured legs of patients with ACL tear, without or before surgery. Thirteen studies were included in the meta-analysis. Quadriceps and hamstring strengths were 22.3 N∙m (95% CI: 15.2 to 29.3 N∙m; P<0.001) and 7.4 N∙m (95% CI: 4.3 to 10.5 N∙m; P<0.001) lower, respectively, on the injured than on the uninjured side. The mean hamstring-to-quadriceps ratio was 4% greater in ACL deficient than in uninjured limbs (95% CI: 1.7% to 6.3%; P<0.001). Conclusively, Decreases were observed in both the quadriceps and hamstring muscles of patients with ACL tear, with the decrease in quadriceps strength being 3-fold greater. These uneven reductions slightly increase the hamstring-to-quadriceps ratio in ACL deficient knees.
authors.affiliation: Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Sports Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jin-Hyuck
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Sports Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Sung-Eun
authors.initials: SE
authors.lastname: Ahn
authors.affiliation: Department of Sports Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Min-Ji
authors.initials: MJ
authors.lastname: Park
authors.affiliation: Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Dae-Hee
authors.initials: DH
authors.lastname: Lee
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D053580:Muscle Strength; D052097:Quadriceps Muscle / Q000503:physiopathology*; D016059:Range of Motion, Articular; D016896:Treatment Outcome