Differences in Isokinetic Strength of the Knee Extensors and Flexors in Men With Isolated and Combined Cruciate-Ligament Knee Injury

Abstract

CONTEXT: The extent of knee extensor and flexor weakness after disruption of knee ligaments affects a rehabilitation output and functional recovery and may give prognostic information on a possible risk of development of knee osteoarthritis. OBJECTIVE: The hypothesis tested was whether patients with a multiple-ligament tear would have larger abnormalities in strength of the knee extensors and flexors than patients with an isolated-ligament rupture. DESIGN: Cross-sectional study, level III. SETTING: Outpatient orthopedic clinic. PARTICIPANTS: 3 groups of recreationally active men: noninjured control (CON, n = 12), with an anterior cruciate ligament injury (ACLI, n = 10), and with combined anterior and posterior cruciate ligament injury (APCLI, n = 9), matched according to age, body mass, and height. INTERVENTION: All patients received conservative treatment and rehabilitation and awaited ligament reconstruction surgery. MAIN OUTCOME MEASURES: Isokinetic maximum-repetition peak torque per body mass (PT/BM) and total work (TW), PT and TW limb-symmetry index (LSI), and flexor-to- extensor PT ratio were evaluated during concentric knee extension-flexion movements at lower (60°/s) and higher (240°/s) isokinetic velocities. RESULTS: The main finding was that compared with the individuals with ACLI, patients with APCLI produced in their injured limbs lower mean TW (extension: 30.3%, flexion: 28.2%) and had lower mean TW LSI (extension 74% in APCLI vs. 91.6% in ACLI; flexion 61.3% in APCLI vs. 90.8% in ACLI) at the higher but not lower speed of isokinetic testing. However, at the lower velocity the quantified size of reduction in PT/BM and TW was greater in subjects with APCLI than ACLI as compared with the CON individuals. CONCLUSIONS: After bi-cruciate-ligament injury the capacity to produce torque by concentric muscle contractions throughout knee-extension and -flexion movements performed with high speed is lower in injured limbs than after isolated anterior cruciate ligament tear.