title: Bone marrow changes related to disuse.
abstract: OBJECTIVE
  To evaluate bone marrow changes on knee magnetic resonance imaging (MRI) in patients with 3- to 6-week-long period of unloading.
  
  
  METHODS
  MRI knee examinations were performed in 30 patients (14 men, 16 women; aged 20-53 years) at baseline and 5-10 weeks after immobilisation of the ipsilateral lower extremity; subsets of patients were examined at additional time-points. Ten volunteers (4 men, 6 women; aged 20-50 years) were studied as control cohort at two time-points. Bone marrow signal abnormalities were analysed according to: (1) severity, (2) signal alteration relative to hyaline cartilage, (3) morphology, (4) increased vascularity in the knee joint and (5) T1-signal alteration. Spearman's rank correlation test (SRC) and Kendall's tau (KT) were used to compare individual scores.
  
  
  RESULTS
  All 30 patients presented abnormal bone marrow findings after unloading, which reached a peak at 10-25 weeks (P <0.001). These findings decreased within 1 year (P < 0.001). High scores of severity were associated with confluent and patchy patterns of bone marrow (SCR = 0.923, P < 0.001 and KT = 0.877, P <0.001).
  
  
  CONCLUSIONS
  Signal abnormalities of the bone marrow related to unloading are consistent findings and most prominent 10-25 weeks following immobilisation when both confluent and patchy hyperintense patterns are present.
authors.affiliation: Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology, University of California, San Francisco, San Francisco, CA, USA, Lorenzo.Nardo@ucsf.edu.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Nardo
authors.forename: David N
authors.initials: DN
authors.lastname: Sandman
authors.forename: Warapat
authors.initials: W
authors.lastname: Virayavanich
authors.forename: Linlin
authors.initials: L
authors.lastname: Zhang
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
authors.forename: Lynne
authors.initials: L
authors.lastname: Steinbach
authors.forename: Michele
authors.initials: M
authors.lastname: Guindani
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
mesh_terms: D000328:Adult; D064386:Ankle Fractures; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D001853:Bone Marrow / Q000473:pathology*; D004434:Early Ambulation; D005260:Female; D005269:Femur / Q000098:blood supply / Q000473:pathology; D005500:Follow-Up Studies; D018409:Foot Injuries / Q000601:surgery; D006801:Humans; D007103:Immobilization; D007719:Knee Joint / Q000098:blood supply / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020966:Muscular Disorders, Atrophic / Q000473:pathology*; D010329:Patella / Q000098:blood supply / Q000473:pathology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013977:Tibia / Q000098:blood supply / Q000473:pathology; D016474:Weight-Bearing; D055815:Young Adult