title: Granulomatous inflammation after Hylan G-F 20 viscosupplementation of the knee : a report of six cases.
abstract: BACKGROUND
  Recently, intra-articular viscosupplementation with hyaluronate-derived products has gained popularity as a palliative modality for the treatment of osteoarthritis of the knee. Mild pain or swelling at the site of injection may occur in up to 20% of patients, although severe local inflammation, warmth, and joint effusion are rare. We present a series of six cases in which granulomatous inflammation of the synovium was observed after hyaluronate viscosupplementation of the knee.
  
  
  METHODS
  Six knees (five patients) treated with intra-articular Hylan G-F 20 viscosupplementation underwent a surgical procedure because of persistent symptoms. Routine histopathological evaluation, supplemented by alcian-blue staining and hyaluronidase digestion, was performed in each case.
  
  
  RESULTS
  Chronically inflamed synovium with areas of histiocytic and foreign-body giant-cell reaction was observed surrounding acellular, amorphous material. The material stained with alcian blue, a stain for hyaluronate, which disappeared after hyaluronidase digestion.
  
  
  CONCLUSIONS
  We believe that the injected hyaluronate (Hylan G-F 20) may have been responsible for the synovitis in our patients and thus may be a pathological cause of recalcitrant symptoms after such injection. It is not known whether the responsible pathological agent was the hyaluronate derivative, a contaminant of the purification process, or a component of the carrier substance. Importantly, it appears that the findings in these patients most likely represent a previously unreported pathological response to a viscosupplementation product. This report should raise clinical awareness about this potential complication.
authors.affiliation: Department of Orthopaedic Surgery, New York University-Hospital for Joint Diseases, New York, NY 10003, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Chen
authors.forename: Panna
authors.initials: P
authors.lastname: Desai
authors.forename: Edward M
authors.initials: EM
authors.lastname: Adler
authors.forename: Paul E
authors.initials: PE
authors.lastname: Di Cesare
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D015745:Granuloma, Foreign-Body / Q000139:chemically induced* / Q000473:pathology; D006801:Humans; D006820:Hyaluronic Acid / Q000008:administration & dosage / Q000009:adverse effects* / Q000031:analogs & derivatives*; D007270:Injections, Intra-Articular; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000628:therapy*; D013585:Synovitis / Q000139:chemically induced* / Q000473:pathology
chemical_list: C049816:hylan; D006820:Hyaluronic Acid