title: Frontal plane knee mechanics and medial cartilage MR relaxation times in individuals with ACL reconstruction: A pilot study.
abstract: BACKGROUND
  The objective of this pilot study was to evaluate cartilage T1ρ and T2 relaxation times and knee mechanics during walking and drop-landing for individuals with anterior cruciate ligament reconstruction (ACL-R).
  
  
  METHODS
  Nine patients (6 men and 3 women, age 35.8 ± 5.4 years, BMI 23.5 ± 2.5 kg/m(2)) participated 1.5 ± 0.8 years after single-bundle two-tunnel ACL reconstruction. Peak knee adduction moment (KAM), flexion moment (KFM), extension moment (KEM), and peak varus were calculated from kinematic and kinetic data obtained during walking and drop-landing tasks. T1ρ and T2 times were calculated for medial femur (MF), and medial tibia (MT) cartilage and compared between subjects with low KAM and high KAM. Biomechanical variables were compared between limbs.
  
  
  RESULTS
  The high KAM group had higher T1ρ for MT (p=0.01), central MT (p=0.05), posterior MF (p=0.04), posterior MT (p=0.01); and higher T2 for MT (p=0.02), MF (p=0.05), posterior MF (p=0.002) and posterior MT (p=0.01). During walking, ACL-R knees had greater flexion at initial contact (p=0.04), and lower KEM (p=0.02). During drop-landing, the ACL-R knees had lower KAM (p=0.03) and KFM (p=0.002).
  
  
  CONCLUSIONS
  Patients with ACL-R who have higher KAM during walking had elevated MR relaxation times in the medial knee compartments. These data suggest that those individuals who have undergone ACL-R and have higher frontal plane loading, may be at a greater risk of knee osteoarthritis.
authors.affiliation: Department of Radiology and Biomedical Imaging, UCSF, United States. Electronic address: krdeepak2pro@gmail.com.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.affiliation: Department of Radiology and Biomedical Imaging, UCSF, United States.
authors.forename: Abbas
authors.initials: A
authors.lastname: Kothari
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, United States; Department of Orthopaedic Surgery, UCSF, United States.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
authors.affiliation: Department of Radiology and Biomedical Imaging, UCSF, United States.
authors.forename: Samuel
authors.initials: S
authors.lastname: Wu
authors.affiliation: Department of Orthopaedic Surgery, UCSF, United States.
authors.forename: C
authors.initials: C
authors.lastname: Benjamin Ma
authors.affiliation: Department of Radiology and Biomedical Imaging, UCSF, United States.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Li
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D002358:Cartilage, Articular / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D010865:Pilot Projects; D016059:Range of Motion, Articular / Q000502:physiology; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
keywords: Drop-landing; Gait; Knee adduction moment; T(1ρ); T(2)