title: Imaging of synovitis in osteoarthritis: current status and outlook.
abstract: OBJECTIVE
  This review article provides an overview of the current state of imaging of synovitis in osteoarthritis (OA), looking at recent advances and controversies and focusing particularly on the application of ultrasound and magnetic resonance imaging (MRI) in the assessment of the hand and knee joint. Computed tomography and nuclear medicine including positron emission tomography are also briefly discussed.
  
  
  METHODS
  PubMed and MEDLINE search for articles published up to 2010, using the keywords synovitis, osteoarthritis, rheumatoid arthritis, pathogenesis, imaging, radiography, computed tomography, nuclear medicine, magnetic resonance imaging, ultrasound, and pain.
  
  
  RESULTS
  Synovitis is defined as inflammation of the synovial membrane. Modern imaging techniques have demonstrated that synovial pathology is common in the early and late stages of OA and may be associated with pain. The current standard for OA imaging in clinical practice is conventional radiography but it does not allow direct visualization of synovitis. MRI without contrast administration, although widely used in clinical studies, cannot assess synovitis directly. Contrast-enhanced MRI and ultrasound, however, both allow direct visualization of synovitis including early inflammatory changes. They are regularly used to image synovitis in rheumatoid arthritis and increasingly in OA.
  
  
  CONCLUSIONS
  Synovitis is increasingly recognized as an important feature of the pathophysiology of OA, although there is conflicting evidence with respect to its association with disease severity and clinical parameters. Contrast-enhanced MRI and ultrasound are the most important methods for assessing synovitis associated with OA.
authors.affiliation: Department of Radiology, Boston University School of Medicine, Boston, MA, USA. dhayashi@bu.edu
authors.forename: Daichi
authors.initials: D
authors.lastname: Hayashi
authors.forename: Frank W
authors.initials: FW
authors.lastname: Roemer
authors.forename: Avinash
authors.initials: A
authors.lastname: Katur
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Seoung-Oh
authors.initials: SO
authors.lastname: Yang
authors.forename: Faris
authors.initials: F
authors.lastname: Alomran
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
mesh_terms: D003952:Diagnostic Imaging; D050823:Hand Joints / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology; D010003:Osteoarthritis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography; D013583:Synovial Membrane / Q000000981:diagnostic imaging / Q000473:pathology; D013585:Synovitis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D014463:Ultrasonography