title: Trajectory of cartilage loss within 4 years of knee replacement--a nested case-control study from the osteoarthritis initiative.
abstract: OBJECTIVE
  Knee replacement (KR) represents a clinically important endpoint of knee osteoarthritis (KOA). Here we examine the 4-year trajectory of femoro-tibial cartilage thickness loss prior to KR vs non-replaced controls.
  
  
  METHODS
  A nested case-control study was performed in Osteoarthritis Initiative (OAI) participants: Cases with KR between 12 and 60 month (M) follow-up were each matched with one control (without KR through 60M) by age, sex, and baseline radiographic stage. Femoro-tibial cartilage thickness was measured quantitatively using magnetic resonance imaging (MRI) at the annual visit prior to KR occurrence (T0), and at 1-4 years prior to T0 (T-1 to T-4). Cartilage loss between cases and controls was compared using paired t-tests and conditional logistic regression.
  
  
  RESULTS
  One hundred and eighty-nine knees of 164 OAI participants [55% women; age 64 ± 8.7; body mass index (BMI) 29 ± 4.5] had KR and longitudinal cartilage data. Comparison of annualized slopes of change across all time points revealed greater loss in the central medial tibia (primary outcome) in KRs than in controls [94 ± 137 vs 55 ± 104 μm; P = 0.0017 (paired t); odds ratio (OR) 1.36 (95% confidence interval (CI): 1.08-1.70)]. The discrimination was stronger for T-2 → T0 [OR 1.61 (1.33-1.95), n = 127] than for T-1 → T0, and was not statistically significant for intervals prior to T-2 [i.e., T-4 → T-2, OR 0.97 (0.67-1.41), n = 60]. Results were similar for total medial femoro-tibial cartilage loss (secondary outcome), and when adjusting for pain and BMI.
  
  
  CONCLUSIONS
  In knees with subsequent replacement, cartilage loss accelerates in the 2 years, and particularly in the year prior to surgery, compared with controls. Whether slowing this cartilage loss can delay KR remains to be determined.
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany. Electronic address: felix.eckstein@pmu.ac.at.
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
authors.affiliation: Department of Epidemiology, Grad. Sch. of Public Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Boudreau
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hannon
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Cotofana
authors.affiliation: Department of Radiology, Boston University School of Medicine & Boston Imaging Core Lab (BICL), LLC, Boston, MA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Guermazi
authors.affiliation: Department of Radiology, Boston University School of Medicine & Boston Imaging Core Lab (BICL), LLC, Boston, MA, USA; Department of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Roemer
authors.affiliation: OAI Coordinating Ctr., UCSF, San Francisco, CA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.affiliation: Novartis Pharma AG, Basel, Switzerland.
authors.forename: M R
authors.initials: MR
authors.lastname: John
authors.affiliation: Merck KGaA, Darmstadt, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ladel
authors.affiliation: Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: L
authors.initials: L
authors.lastname: Sharma
authors.affiliation: Royal North Shore Hospital & Northern Clinical School, University Sydney, Sydney, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Hunter
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Division of Rheumatology and University of Arizona Arthritis Center, University of Arizona College of Medicine, Tucson, AZ, USA.
authors.forename: C K
authors.initials: CK
authors.lastname: Kwoh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D002357:Cartilage Diseases / Q000209:etiology / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology* / Q000601:surgery
keywords: Cartilage loss; Knee arthroplasty; Knee osteoarthritis; Knee replacement; Magnetic resonance imaging