Axial knee radiographs: Consistency across clinic sites

Ashley Nord, Julie Agel, Elizabeth A. Arendt

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Conclusions: Radiographic protocols for knee axial imaging are inconsistent in radiographic positioning and imaging. This variability can lead to disparity in radiographic image results used for clinical decision-making. Standardization of radiographic positioning would yield more consistent imaging of patella position in early flexion, increasing clinical utility and accuracy.


Methods: Radiographic positioning, including beam angle and knee flexion, was measured using a photograph taken of a phantom leg and (human) model set-up. An axial radiograph of a phantom leg was taken at seven different outpatients musculoskeletal clinics to assess patella position (lateral tilt/translation). The phantom leg patella was placed in an abnormal position for the radiographic image across all sites.

Results: Knee flexion <30° was less accurate in obtaining requested knee flexion than higher knee flexion angles (phantom limb error averaged 6°, range 4°–7° human model error averaged 15°, range 11°–25°). Of the five sites utilizing a ‘Merchants’ axial radiographs, the congruence angle varied from +12° to +29°, being normal at one site (+12°) and abnormal (>+16°) at three sites, and negative at one site (−15°).

Original languageEnglish (US)
Pages (from-to)2401-2407
Number of pages7
JournalKnee Surgery, Sports Traumatology, Arthroscopy
Issue number10
StatePublished - Sep 1 2014

Bibliographical note

Publisher Copyright:
© 2014, Springer-Verlag Berlin Heidelberg.


  • Axial radiograph
  • Patella imaging
  • Patella tilt


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