title: Cartilage and bone markers and inflammatory cytokines are increased in synovial fluid in the acute phase of knee injury (hemarthrosis)--a cross-sectional analysis.
abstract: OBJECTIVE
  The aim of this cross-sectional study was to investigate concentrations of cartilage and bone markers, and pro-inflammatory cytokines in synovial fluid (SF) collected at different time-points from acutely injured knees with hemarthrosis and to compare these with SF concentrations of knees of age and gender-matched healthy reference subjects.
  
  
  METHODS
  SF was aspirated from the acutely injured knee of 111 individuals (mean age 27 years, span 13-64 years, 22% women). Concentrations of sulfated glycosaminoglycan (sGAG) were measured by Alcian blue precipitation whereas cartilage ARGS, bone biomarkers [osteocalcin (OCL), secreted protein acidic and rich in cysteine (SPARC) and osteopontin (OPN)] and pro-inflammatory cytokines [interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor (TNF)-α] were analyzed using electrochemiluminescence. Samples were also analyzed with regard to time between injury and aspiration [same day (n = 29), 1 day (n = 31), 2-3 days (n = 19), 4-7 days (n = 20) and 8-23 days (n = 12)].
  
  
  RESULTS
  SF concentrations of ARGS (P < 0.001), SPARC (P < 0.001), OPN (P < 0.001), and all cytokines (P < 0.001), but not sGAG (P = 0.06) or OCL (P = 0.992), were significantly higher in injured knees compared to knees of reference subjects. The cartilage markers sGAG and ARGS were significantly higher in knees aspirated later than 1 day after injury, whereas concentrations of SPARC and OPN and all cytokines were higher in knees aspirated the same day as the injury and at all time-points thereafter.
  
  
  CONCLUSIONS
  Our results suggest that an acute knee injury is associated with an instant local biochemical response to the trauma, which may affect cartilage and bone as well as the inflammatory activity.
authors.affiliation: Department of Orthopaedics, Clinical Sciences Lund, Lund University, Lund, Sweden. per.sward@med.lu.se
authors.forename: P
authors.initials: P
authors.lastname: Swärd
authors.forename: R
authors.initials: R
authors.lastname: Frobell
authors.forename: M
authors.initials: M
authors.lastname: Englund
authors.forename: H
authors.initials: H
authors.lastname: Roos
authors.forename: A
authors.initials: A
authors.lastname: Struglics
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D053674:Aggrecans / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism*; D002358:Cartilage, Articular / Q000378:metabolism*; D003430:Cross-Sectional Studies; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D006395:Hemarthrosis / Q000209:etiology / Q000378:metabolism*; D006801:Humans; D007718:Knee Injuries / Q000150:complications / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D013582:Synovial Fluid / Q000378:metabolism*; D013997:Time Factors; D055815:Young Adult
chemical_list: D053674:Aggrecans; D015415:Biomarkers; D016207:Cytokines