title: Pigmented villonodular synovitis of the knee in a patient on oral anticoagulation therapy: a case report.
abstract: BACKGROUND
  Pigmented villonodular synovitis is a disease which affects the synovial joints and tendon sheaths. Although the exact aetiological factors are not known, we believe that recurrent haemarthrosis has a role in the aetiology of this condition.
  
  
  METHODS
  A 62-year-old Caucasian man presented with gradually worsening pain and stiffness in his right knee. The patient was on anticoagulation therapy and had been treated for recurrent episodes of spontaneous haemarthrosis of the knee. The International Normalized Ratio on each occasion suggested poor control of the anticoagulation therapy. A diagnosis of pigmented villonodular synovitis was made based on intra-operative findings and was further confirmed by a histopathological examination.
  
  
  CONCLUSIONS
  This report is presented to highlight the unusual association of haemarthrosis and pigmented villonodular synovitis.
authors.affiliation: Department of Trauma and Orthopaedics, Glan Clwyd Hospital, Sarn Lane, Bodelwyddan, Rhyl, North Wales, LL18 5UJ, UK.
authors.forename: Balasundaram
authors.initials: B
authors.lastname: Ramesh
authors.forename: Sanathkumar
authors.initials: S
authors.lastname: Shetty
authors.forename: Salah S
authors.initials: SS
authors.lastname: Bastawrous