title: Potential role of the posterior cruciate ligament synovio-entheseal complex in joint effusion in early osteoarthritis: a magnetic resonance imaging and histological evaluation of cadaveric tissue and data from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  This study explored posterior cruciate ligament (PCL) synovio-entheseal complex (SEC) microanatomy to determine whether it may participate in the early osteoarthritis (OA) disease process.
  
  
  METHODS
  SEC microanatomy and OA features were evaluated in 14 non-arthritic cadaveric knees (mean age = 69.9) using magnetic resonance imaging (MRI) and histology. MRI images of 49 subjects selected from the progression cohort of the Osteoarthritis Initiative (OAI) were evaluated by a musculoskeletal radiologist using an original semi-quantitative method for features associated with OA at the PCL tibial enthesis. Statistical analysis was performed using chi-square and Wilcoxon signed-rank tests to evaluate associations between SEC configuration and OA features.
  
  
  RESULTS
  The PCL formed a SEC-like structure encompassing bone- and ligament-lining intra-articular cartilages to which the posterior root of the medial meniscus contributed. Degenerative features at the PCL-SEC included: neovascularisation (44%), enthesis chondrocyte clustering (44%), collagen matrix fissuring at the enthesis (56%) and in the PCL itself (67%), tidemark duplication (44%), bone remodelling (44%) and microscopic inflammatory changes (33%). In the OAI cohort, SEC-related pathology included bone marrow lesions (BMLs) (69%) and osteophytosis (94%) at locations that corresponded to SEC-related cartilages. Posterior joint recess effusion (49%) was linked to MRI abnormalities at PCL-SEC cartilages (χ2 = 7.27, P = 0.007).
  
  
  CONCLUSIONS
  The PCL has a prominent SEC configuration that is associated with microscopic OA changes in aged clinically non-diseased joints. MRI determined knee OA commonly exhibited pathological features at this site which was associated with adjacent joint effusion. Thus, the PCL-SEC could play a hitherto unappreciated role in the early OA disease process.
authors.affiliation: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK; Leeds NIHR Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Electronic address: d.a.binks@leeds.ac.uk.
authors.forename: D A
authors.initials: DA
authors.lastname: Binks
authors.affiliation: Department of Radiology, Galway University Hospitals, Galway, Ireland. Electronic address: dianebergin@yahoo.com.
authors.forename: D
authors.initials: D
authors.lastname: Bergin
authors.affiliation: School of Medicine, University of Manchester, Manchester, UK. Electronic address: tony.freemont@manchester.ac.uk.
authors.forename: A J
authors.initials: AJ
authors.lastname: Freemont
authors.affiliation: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK; Leeds NIHR Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Electronic address: richardhodgson@btinternet.com.
authors.forename: R J
authors.initials: RJ
authors.lastname: Hodgson
authors.affiliation: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK; Leeds NIHR Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Electronic address: takep0511@yahoo.co.jp.
authors.forename: T
authors.initials: T
authors.lastname: Yonenaga
authors.affiliation: Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK; Leeds NIHR Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Electronic address: d.g.mcgonagle@leeds.ac.uk.
authors.forename: D
authors.initials: D
authors.lastname: McGonagle
authors.affiliation: Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK. Electronic address: Aleksandra.radjenovic@glasgow.ac.uk.
authors.forename: A
authors.initials: A
authors.lastname: Radjenovic
mesh_terms: D000368:Aged; D002102:Cadaver; D002358:Cartilage, Articular / Q000473:pathology; D005122:Exudates and Transudates; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D016119:Posterior Cruciate Ligament / Q000473:pathology*; D013583:Synovial Membrane / Q000473:pathology*; D013585:Synovitis / Q000473:pathology; D013710:Tendons / Q000473:pathology
keywords: Enthesis; Knee OA; MRI; Synovitis