Skeletal Radiology

, Volume 42, Issue 11, pp 1573–1582 | Cite as

Minimum joint space width (mJSW) of patellofemoral joint on standing “skyline” radiographs: test-retest reproducibility and comparison with quantitative magnetic resonance imaging (qMRI)

  • Paolo SimoniEmail author
  • Sanaa Jamali
  • Adelin Albert
  • Saara Totterman
  • Edward Schreyer
  • Jose G. Tamez-Peña
  • Bruno Beomonte Zobel
  • Victoria Alvarez Miezentseva
  • Philippe Gillet
Scientific Article



To assess the intraobserver, interobserver, and test-retest reproducibility of minimum joint space width (mJSW) measurement of medial and lateral patellofemoral joints on standing “skyline” radiographs and to compare the mJSW of the patellofemoral joint to the mean cartilage thickness calculated by quantitative magnetic resonance imaging (qMRI).

Materials and methods

A couple of standing “skyline” radiographs of the patellofemoral joints and MRI of 55 knees of 28 volunteers (18 females, ten males, mean age, 48.5 ± 16.2 years) were obtained on the same day. The mJSW of the patellofemoral joint was manually measured and Kellgren and Lawrence grade (KLG) was independently assessed by two observers. The mJSW was compared to the mean cartilage thickness of patellofemoral joint calculated by qMRI.


mJSW of the medial and lateral patellofemoral joint showed an excellent intraobserver agreement (interclass correlation (ICC) = 0.94 and 0.96), interobserver agreement (ICC = 0.90 and 0.95) and test-retest agreement (ICC = 0.92 and 0.96). The mJSW measured on radiographs was correlated to mean cartilage thickness calculated by qMRI (r = 0.71, p < 0.0001 for the medial PFJ and r = 0.81, p < 0.0001 for the lateral PFJ). However, there was a lack of concordance between radiographs and qMRI for extreme values of joint width and KLG. Radiographs yielded higher joint space measures than qMRI in knees with a normal joint space, while qMRI yielded higher joint space measures than radiographs in knees with joint space narrowing and higher KLG.


Standing “skyline” radiographs are a reproducible tool for measuring the mJSW of the patellofemoral joint. The mJSW of the patellofemoral joint on radiographs are correlated with, but not concordant with, qMRI measurements.


Patellofemoral joint Radiography Magnetic resonance imaging Articular cartilage Osteoarthritis knee Radiography Adult 


Conflict of interest

The authors declare that there are no conflicts of interest.


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Copyright information

© ISS 2013

Authors and Affiliations

  • Paolo Simoni
    • 1
    Email author
  • Sanaa Jamali
    • 1
  • Adelin Albert
    • 2
  • Saara Totterman
    • 3
  • Edward Schreyer
    • 3
  • Jose G. Tamez-Peña
    • 3
  • Bruno Beomonte Zobel
    • 4
  • Victoria Alvarez Miezentseva
    • 1
  • Philippe Gillet
    • 5
  1. 1.Diagnostic Imaging Departement, Domanine du Sart TilmanCHU de LiègeLiègeBelgium
  2. 2.Biostatistics Departement, Domanine du Sart TilmanCHU de LiègeLiègeBelgium
  3. 3.Qmetrics Technologies140 Allens Creek RoadRochesterUSA
  4. 4.Diagnostic Imaging DepartementCampus Bio-Medico UniversityRomeItaly
  5. 5.Orthopaedic surgery Department, Domanine du Sart TilmanCHU de LiègeLiègeBelgium

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