title: Inflammation is more distinct in temporomandibular joint osteoarthritis compared to the knee joint.
abstract: OBJECTIVE
  Most of the current understanding of articular cartilage maintenance and degradation is derived from large load-bearing synovial joints, in particular the knee joint. The aim of this study was to identify valuable degradation markers for cartilage degradation in the temporomandibular joint (TMJ) by comparing the relative concentrations of carboxyterminal telopeptides of collagen types I and II (CTX-I and CTX-II), cartilage oligomeric matrix protein (COMP), and prostaglandin E2 (PGE2) in synovial fluid (SF) of TMJ and knee joints with cartilage degradation.
  
  
  METHODS
  In this cross-sectional comparative study, participants were recruited from the University Medical Center Groningen, The Netherlands. Patients with TMJ osteoarthritis were compared with patients with knee osteoarthritis. The outcome variables were the relative SF concentrations of CTX-I, CTX-II, COMP, and PGE2. An independent samples Mann-Whitney U test was used to compare the relative concentrations.
  
  
  RESULTS
  Thirty consecutive patients (9 male, 21 female; mean age, 40.1 yr; standard deviation, 15.3 yr) with TMJ osteoarthritis and 31 consecutive patients (20 male, 11 female; mean age, 37.4 yr; standard deviation, 13.7 yr) who were scheduled for arthroscopy of the knee joint participated in this study. Significant differences were found between relative concentrations of COMP (P = .000) and PGE2 (P = .005), and no significant differences were found between relative concentrations of CTX-I (P = .720) and CTX-II (P = .242).
  
  
  CONCLUSIONS
  Relative SF concentrations of COMP and PGE2 showed significant differences between the TMJ and the knee joint, suggesting that there are differences in pathophysiology and that the inflammatory component may be more distinct in the TMJ.
authors.affiliation: Research Assistant, Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Electronic address: l.m.vos@umcg.nl.
authors.forename: Lukas M
authors.initials: LM
authors.lastname: Vos
authors.affiliation: Senior Researcher, Department of Biomaterials, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Roel
authors.initials: R
authors.lastname: Kuijer
authors.affiliation: Senior Researcher, Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: James J R
authors.initials: JJ
authors.lastname: Huddleston Slater
authors.affiliation: Professor, Department of Orthopedics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Sjoerd K
authors.initials: SK
authors.lastname: Bulstra
authors.affiliation: Professor, Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Boudewijn
authors.initials: B
authors.lastname: Stegenga
mesh_terms: D000328:Adult; D001182:Arthroscopy / Q000379:methods; D064236:Cartilage Oligomeric Matrix Protein / Q000032:analysis; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology; D024042:Collagen Type I / Q000032:analysis; D024043:Collagen Type II / Q000032:analysis; D003430:Cross-Sectional Studies; D015232:Dinoprostone / Q000032:analysis; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D008297:Male; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology*; D020370:Osteoarthritis, Knee / Q000378:metabolism / Q000473:pathology*; D019152:Paracentesis / Q000379:methods; D010455:Peptides / Q000032:analysis; D013582:Synovial Fluid / Q000737:chemistry; D013705:Temporomandibular Joint Disorders / Q000378:metabolism / Q000473:pathology*
chemical_list: D064236:Cartilage Oligomeric Matrix Protein; D024042:Collagen Type I; D024043:Collagen Type II; D015232:Dinoprostone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; C577553:TSP5 protein, human