Fixed-flexion radiography of the knee provides reproducible joint space width measurements in osteoarthritis

Eur Radiol. 2004 Sep;14(9):1568-73. doi: 10.1007/s00330-004-2312-6. Epub 2004 May 19.


The validity of a non-fluoroscopic fixed-flexion radiographic acquisition and analysis protocol for measurement of joint space width (JSW) in knee osteoarthritis is determined. A cross-sectional study of 165 patients with documented knee osteoarthritis participating in a multicenter, prospective study of chondroprotective agents was performed. All patients had posteroanterior, weight-bearing, fixed-flexion radiography with 10 degrees caudal beam angulation. A specially designed frame (SynaFlexer) was used to standardize the positioning. Minimum medial and lateral JSW were measured manually and twice by an automated analysis system to determine inter-technique and intra-reader concordance and reliability. A random subsample of 30 patients had repeat knee radiographs 2 weeks apart to estimate short-term reproducibility using automated analysis. Concordance between manual and automated medial JSW measurements was high (ICC=0.90); lateral compartment measurements showed somewhat less concordance (ICC=0.72). There was excellent concordance between repeated automated JSW measurements performed 6 months apart for the medial (ICC=0.94) and lateral (ICC=0.86) compartments. Short-term reproducibility for the subsample of 30 cases with repeat acquisitions demonstrated an average SD of 0.14 mm for medial JSW (CV=4.3%) and 0.23 mm for lateral JSW (CV=4.0%). Fixed-flexion radiography of the knee using a positioning device provides consistent, reliable and reproducible measurement of minimum JSW in knee osteoarthritis without the need for concurrent fluoroscopic guidance.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Arthrography / standards*
  • Calibration
  • Female
  • Humans
  • Image Processing, Computer-Assisted / standards*
  • Knee Joint / diagnostic imaging*
  • Knee Joint / drug effects
  • Male
  • Middle Aged
  • Osteoarthritis, Knee / diagnostic imaging*
  • Phantoms, Imaging
  • Prospective Studies
  • Range of Motion, Articular / drug effects
  • Range of Motion, Articular / physiology*
  • Reference Values
  • Reproducibility of Results
  • Weight-Bearing / physiology*