title: Synovial fluid concentrations of the C-propeptide of type II collagen correlate with body mass index in primary knee osteoarthritis.
abstract: OBJECTIVE
  To explore in a cross sectional study in patients with primary knee osteoarthritis (OA) the relations between body mass index (BMI), disease stage, and the concentrations of a putative joint fluid marker of type II collagen synthesis, procollagen II C-propeptide.
  
  
  METHODS
  The study included 142 patients with knee OA (median age 68, median BMI 24.1). OA was staged radiologically. The concentrations in synovial fluid of procollagen II C-propeptide were measured by a sandwich enzyme immunoassay.
  
  
  RESULTS
  Joint fluid concentrations of procollagen II C-propeptide were increased in knees with OA (median 3.7 ng/ml), compared with published reference values for knees in healthy adult volunteers (median 1.3 ng/ml). The concentrations of procollagen II C-propeptide were independently related to both OA stage and BMI (r = 0.343, p < 0.0001 and r, = 0.253, p = 0.002, respectively).
  
  
  CONCLUSIONS
  Joint fluid concentrations of this putative marker of collagen II synthesis are high in early and mid-stage OA, but decrease in end stage disease. In addition and for the first time it was shown that the concentrations in synovial fluid of procollagen II C-propeptide increase with increasing BMI in primary knee OA. The increased joint fluid values of this marker in patients with primary knee OA and a high BMI, may reflect increased rates of collagen synthesis in their joint cartilage and could relate to the previously shown increased risk for disease progression in such patients.
authors.affiliation: Department of Orthopaedic Surgery, National Defence Medical College, Tokorozawa, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshihara
authors.forename: A
authors.initials: A
authors.lastname: Samura
authors.forename: H
authors.initials: H
authors.lastname: Yamada
authors.forename: M
authors.initials: M
authors.lastname: Shinmei
authors.forename: H
authors.initials: H
authors.lastname: Roos
authors.forename: L S
authors.initials: LS
authors.lastname: Lohmander
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015415:Biomarkers / Q000032:analysis; D015992:Body Mass Index; D002135:Calcium-Binding Proteins / Q000032:analysis*; D003094:Collagen / Q000032:analysis*; D024043:Collagen Type II; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000378:metabolism*; D011498:Protein Precursors / Q000032:analysis*; D011859:Radiography; D012044:Regression Analysis; D012307:Risk Factors; D013582:Synovial Fluid / Q000737:chemistry*
chemical_list: D015415:Biomarkers; D002135:Calcium-Binding Proteins; D024043:Collagen Type II; D011498:Protein Precursors; C040072:chondrocalcin; D003094:Collagen