title: Osteoarthritic bone marrow lesions almost exclusively colocate with denuded cartilage: a 3D study using data from the Osteoarthritis Initiative.
abstract: The aetiology of bone marrow lesions (BMLs) in knee osteoarthritis (OA) is poorly understood. We employed three-dimensional (3D) active appearance modelling (AAM) to study the spatial distribution of BMLs in an OA cohort and compare this with the distribution of denuded cartilage.
  
  
  
  Participants were selected from the Osteoarthritis Initiative progressor cohort with Kellgren-Lawrence scores ≥2, medial joint space narrowing and osteophytes. OA and ligamentous BMLs and articular cartilage were manually segmented. Bone surfaces were automatically segmented by AAM. Cartilage thickness of <0.5 mm was defined as denuded and ≥0.5-1.5 mm as severely damaged. Non-quantitative assessment and 3D population maps were used for analysing the comparative position of BMLs and damaged cartilage.
  
  
  
  88 participants were included, 45 men, mean age (SD) was 61.3 (9.9) years and mean body mass index was 31.1 (4.6) kg/m(2). 227 OA and 107 ligamentous BMLs were identified in 86.4% and 73.8% of participants; OA BMLs were larger. Denuded cartilage was predominantly confined to a central region on the medial femur and tibia, and the lateral facet of the trochlear femur. 67% of BMLs were colocated with denuded cartilage and a further 21% with severe cartilage damage. In the remaining 12%, 25/28 were associated with cartilage defects. 74% of all BMLs were directly opposing (kissing) another BML across the joint.
  
  
  
  There was an almost exclusive relationship between the location of OA BML and cartilage denudation, which itself had a clear spatial pattern. We propose that OA, ligamentous and traumatic BMLs represent a bone response to abnormal loading.
authors.affiliation: Imorphics, Manchester, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Bowes
authors.affiliation: Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK.
authors.forename: Stewart Wd
authors.initials: SW
authors.lastname: McLure
authors.affiliation: Imorphics, Manchester, UK.
authors.forename: Christopher Bh
authors.initials: CB
authors.lastname: Wolstenholme
authors.affiliation: Imorphics, Manchester, UK.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Vincent
authors.affiliation: Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK.
authors.forename: Sophie
authors.initials: S
authors.lastname: Williams
authors.affiliation: NIHR Leeds Musculoskeletal Biomedical Research Unit, University of Leeds, Leeds, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Grainger
authors.affiliation: NIHR Leeds Musculoskeletal Biomedical Research Unit, University of Leeds, Leeds, UK Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK.
authors.forename: Philip G
authors.initials: PG
authors.lastname: Conaghan
mesh_terms: D000368:Aged; D001855:Bone Marrow Diseases / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D002357:Cartilage Diseases / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology*; D013977:Tibia / Q000000981:diagnostic imaging / Q000473:pathology
keywords: Disease Activity; Knee Osteoarthritis; Magnetic Resonance Imaging