title: Identifying Hidden Zones of the Far Posterior Cartilage of the Femoral Condyles Not Visible During Knee Arthroscopy.
abstract: OBJECTIVE
  The purpose of this study was to compare standard knee arthroscopic and MRI findings and measurements for visualization of the femoral condyle articular cartilage. The hypothesis was that certain posterior cartilage defects identified with MRI may not be accessible with routine arthroscopy.
  
  
  METHODS
  Six cadaveric knees were examined by routine arthroscopy through standard inferomedial and inferolateral portals. Suture anchors were inserted into the femoral condyles at 30°, 60°, 90°, and 120° of flexion as markers of the cartilage surface at the most posterior aspect of the condyle that could be accessed at each degree of flexion. Each specimen was then examined with 3-T MRI and gross dissection. Measurements were obtained and compared.
  
  
  RESULTS
  During arthroscopy at 90° of knee flexion, only 5.83 mm of the medial femoral condyle and 6.83 mm of the lateral femoral condyle were visualized posterior to the anchor placed at 90° of flexion. These arthroscopic measurements were statistically significant underestimates of the actual amount of cartilage identified posterior to the 90° anchor at gross dissection (medial condyle, 44.20 mm; lateral condyle, 37.50 mm) and MRI (medial, 41.33 mm; lateral, 38.87 mm). This indicates that 85.9% of the medial and 81.8% of the lateral posterior articular cartilage of the femoral condyle seen at MRI were not visualized during arthroscopy.
  
  
  CONCLUSIONS
  More than 80% of the articular cartilage proximal to the menisci seen at MRI is not visible during routine arthroscopy. This far posterior articular cartilage should be called the hidden zone.
authors.affiliation: 1 Orthopaedic Medical Group of Tampa Bay, Tampa, FL.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sando
authors.affiliation: 2 Department of Orthopaedic Surgery, Cedars Sinai Medical Center, 444 San Vicente Blvd, No. 603, Los Angeles, CA 90048.
authors.forename: Sean S
authors.initials: SS
authors.lastname: Rajaee
authors.affiliation: 3 RADNET, Los Angeles, CA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Liu
authors.affiliation: 4 Kerlan-Jobe Orthopaedic Clinic, Los Angeles, CA.
authors.forename: Michael
authors.initials: M
authors.lastname: Banffy
authors.affiliation: 4 Kerlan-Jobe Orthopaedic Clinic, Los Angeles, CA.
authors.forename: Orr
authors.initials: O
authors.lastname: Limpisvasti
authors.affiliation: 3 RADNET, Los Angeles, CA.
authors.forename: John V
authors.initials: JV
authors.lastname: Crues
mesh_terms: D001182:Arthroscopy / Q000379:methods*; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: MRI; arthroscopy; far posterior femoral condyle lesions; knee; posterior cartilage lesions