title: Baseline knee adduction and flexion moments during walking are both associated with 5 year cartilage changes in patients with medial knee osteoarthritis.
abstract: OBJECTIVE
  To test the hypothesis that knee cartilage changes over 5 years are associated with baseline peak knee adduction moment (KAM) and peak knee flexion moment (KFM) during early stance.
  
  
  METHODS
  Baseline KAM and KFM were measured in sixteen subjects with medial knee osteoarthritis (OA). Regional changes in cartilage thickness and changes in medial-to-lateral thickness ratio were quantified using magnetic resonance imaging (MRI) at baseline and again after 5 years. Multiple regression was used to determine whether baseline measures of KAM and KFM were associated with cartilage changes over 5 years. Associations with baseline pain score, Kellgren-Lawrence (KL) grade, walking speed, age, gender, and body mass index (BMI) were tested one-by-one in the presence of KAM and KFM.
  
  
  RESULTS
  Changes over 5 years in femoral medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and pain score (R(2) = 0.60, P = 0.010), and most significantly with KAM (R(2) = 0.33, P = 0.019). Changes in tibial medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.039), with KFM driving this association (R(2) = 0.40, P = 0.009). Changes in medial tibial thickness were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.041); KFM also drove this association (R(2) = 0.42, P = 0.006).
  
  
  CONCLUSIONS
  The findings that the KAM has a greater influence on femoral cartilage change and the KFM has a greater influence on tibial cartilage change provide new insight into the tibiofemoral variations in cartilage changes associated with walking kinetics. These results suggest that both KAM and KFM should be considered when designing disease interventions as well as when assessing the risk for OA progression.
authors.affiliation: Department of Mechanical Engineering, Stanford, CA, United States; Department of Bioengineering, Stanford University, Stanford, CA, United States. Electronic address: echehab@stanford.edu.
authors.forename: E F
authors.initials: EF
authors.lastname: Chehab
authors.affiliation: Department of Mechanical Engineering, Stanford, CA, United States. Electronic address: jfavre@stanford.edu.
authors.forename: J
authors.initials: J
authors.lastname: Favre
authors.affiliation: Department of Mechanical Engineering, Stanford, CA, United States; Palo Alto Veterans Affairs, Palo Alto, CA, United States. Electronic address: jennifer.erhart@gmail.com.
authors.forename: J C
authors.initials: JC
authors.lastname: Erhart-Hledik
authors.affiliation: Department of Mechanical Engineering, Stanford, CA, United States; Palo Alto Veterans Affairs, Palo Alto, CA, United States; Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, CA, United States. Electronic address: tandriac@stanford.edu.
authors.forename: T P
authors.initials: TP
authors.lastname: Andriacchi
mesh_terms: D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D020370:Osteoarthritis, Knee / Q000473:pathology / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012189:Retrospective Studies; D013997:Time Factors; D016138:Walking / Q000502:physiology*
keywords: Ambulatory mechanics; Cartilage thickness; Disease progression; Gait; Kinetics; MRI