title: Extrusion of the medial meniscus in knee osteoarthritis assessed with a rotating clino-orthostatic permanent-magnet MRI scanner.
abstract: OBJECTIVE
  The objectives of this study were to assess the influence of weight-bearing on tibiofemoral osteoarthritis, including medial meniscal extrusion, by using a low-field (0.25 T) rotating clino-orthostatic permanent-magnet magnetic resonance (MR) scanner, and to analyse correlations of medial meniscal extrusion with the patient's Kellgren-Lawrence score, body mass index, and all the osteoarthritis features of the WORMS scoring system.
  
  
  METHODS
  Twenty-six patients (69.2% women and 30.8% men; mean age 67 ± 9.7 years) with medial tibiofemoral knee osteoarthritis were prospectively enrolled and MR sequences were acquired in both clino- and orthostatic position. MR images were assessed by two independent radiologists, according to the WORMS scale. Medial meniscal extrusion was measured and its clino-orthostatic difference (∆MME) was calculated.
  
  
  RESULTS
  Intra- and inter-observer agreement of the WORMS Global Score readings was high by Cohen's K test (>0.81). No significant clino-orthostatic changes in the scoring parameters of the medial tibiofemoral joint were shown by Wilcoxon's test. Medial meniscal extrusion measured on orthostatic images was significantly higher than that measured in clinostatic position (p < 0.0001). At univariate analysis, the Kellgren-Lawrence score, WORMS Global Score, cartilage loss, meniscal damage, and osteophytes were significantly correlated to ∆MME (p < 0.005). Using a multiple regression model, tibiofemoral cartilage loss was found to correlate independently with ∆MME (p = 0.0499).
  
  
  CONCLUSIONS
  Medial meniscal extrusion, evaluated with an open-configuration, rotating MR scanner, increased from the clinostatic to the orthostatic position. ∆MME, a new meniscal parameter, correlated with several important features of medial tibiofemoral osteoarthritis.
authors.affiliation: Department of Radiology, E.O. Ospedali Galliera, Mura della Cappuccine 14, 16128, Genoa, Italy, francesco.paparo@galliera.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paparo
authors.forename: Matteo
authors.initials: M
authors.lastname: Revelli
authors.forename: Riccardo
authors.initials: R
authors.lastname: Piccazzo
authors.forename: Davide
authors.initials: D
authors.lastname: Astengo
authors.forename: Dario
authors.initials: D
authors.lastname: Camellino
authors.forename: Matteo
authors.initials: M
authors.lastname: Puntoni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Muda
authors.forename: Gian Andrea
authors.initials: GA
authors.lastname: Rollandi
authors.forename: Giacomo
authors.initials: G
authors.lastname: Garlaschi
authors.forename: Marco Amedeo
authors.initials: MA
authors.lastname: Cimmino
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D010147:Pain Measurement; D056888:Patient Positioning; D010865:Pilot Projects; D011446:Prospective Studies; D016474:Weight-Bearing