title: Changes of muscle mechanics associated with anterior cruciate ligament deficiency and reconstruction.
abstract: Isometric and isokinetic knee strength deficits were examined on patients with anterior cruciate ligament (ACL) injury before and after ACL reconstruction. Muscle strengths of the uninjured and injured knees were measured from an ACL injured (n = 12) and a control (n = 15) group. Five isometric (10, 30, 50, 70, and 90° of knee flexion) and 5 isokinetic (50, 100, 150, 200, and 250°·s) strengths of quadriceps and hamstrings were measured prereconstruction and postreconstruction (3 and 6 months). Compared with the controls, the uninjured knee showed normal strength and patterns of length-tension and force-velocity relationships. Compared with the uninjured knee, the injured knees showed a generally 25-30% decrease in quadriceps and hamstrings strength with normal patterns of length-tension and force-velocity relationships. By 3 months of reconstruction, weakness of quadriceps of the injured knees was exacerbated, particularly at lengthened positions (∼ 40% of the uninjured knees at knee flexion 70 and 90°) and at slower velocities (∼35% of the uninjured knees at the 50 and 100°·s, p < 0.05), with flattened patterns of mechanical output. By 6 months of reconstruction, the quadriceps of the injured knees still showed significant weakness (∼50% of the uninjured knees) in both contraction types (isometric at knee flexion 90° and isokinetic at 50°·s, p < 0.05). The hamstrings of the injured knees had not shown significant changes after reconstruction. A strengthening program placing emphasis on greater knee flexion angles and slower movement speed with sufficient training duration post ACL reconstruction is recommended because of long-lasting and exacerbated weakness during 3 and 6 months postreconstruction.
authors.affiliation: 1Departments of Physical Therapy, College of Health Sciences; 2Neurology and Master's Program in Neurology, School of Medicine, College of Medicine; 3Department of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital; 4Sports Medicine, College of Medicine; 5Orthopedics, Kaohsiung Medical University, Kaohsiung, Taiwan; 6Department of Orthopedics, School of Medicine, China Medical University; and 7Department of Orthopedic Surgery, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Shih-Fen
authors.initials: SF
authors.lastname: Hsiao
authors.forename: Pei-Hsi
authors.initials: PH
authors.lastname: Chou
authors.forename: Horng-Chaung
authors.initials: HC
authors.lastname: Hsu
authors.forename: Yi-Jing
authors.initials: YJ
authors.lastname: Lue
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007718:Knee Injuries / Q000150:complications / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D053580:Muscle Strength; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D020127:Recovery of Function; D013997:Time Factors; D055815:Young Adult