title: Localized pigmented villonodular synovitis of the knee joint: neoplasm or reactive granuloma? A review of 18 cases.
abstract: OBJECTIVE
  The localized form of pigmented villonodular synovitis of the knee joint is a rare disease with limited alteration of the synovial membrane, the pathogenesis of which is the subject of controversial discussion.
  
  
  METHODS
  Eighteen cases have been documented in our hospital since 1976. All of the patients had additional cartilage or meniscus damage. Treatment consisted of excision of the lesion and the adjacent synovial membrane, as well as therapy of the additional damage.
  
  
  RESULTS
  The patients who had received such therapy were followed for 3-9 yr, without any clinical, sonographic or magnetic resonance tomographic signs of recurrence. In addition to the lack of a tendency towards recurrence, none of the cases displayed any further characteristics of the diffuse form of villonodular synovitis, such as invasiveness or malignant transformation.
  
  
  CONCLUSIONS
  We therefore suggest that pigmented villonodular synovitis of the knee joint should be classified more strictly than before into a potentially neoplastic (diffuse) form and a reactive granulomatous (local) form. From the cases observed, we conclude that degenerative joint lesions may be the cause of the reactive granulomatous form.
authors.affiliation: Department of Orthopaedics and. Department of Rheumatology and Clinical Immunology, Charité University Hospital, Humboldt University, Schumannstrasse 20/21, 10117 Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Perka
authors.forename: K
authors.initials: K
authors.lastname: Labs
authors.forename: H
authors.initials: H
authors.lastname: Zippel
authors.forename: F
authors.initials: F
authors.lastname: Buttgereit
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D005870:Giant Cell Tumors / Q000175:diagnosis*; D006099:Granuloma / Q000175:diagnosis*; D006801:Humans; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012983:Soft Tissue Neoplasms / Q000175:diagnosis*; D000074402:Synovectomy; D013583:Synovial Membrane / Q000473:pathology; D013586:Synovitis, Pigmented Villonodular / Q000175:diagnosis* / Q000601:surgery