Test-retest reliability of tibiofemoral joint space width measurements made using a low-dose standing CT scanner

Skeletal Radiol. 2017 Feb;46(2):217-222. doi: 10.1007/s00256-016-2539-8. Epub 2016 Dec 1.


Objective: To determine the test-retest reliability of knee joint space width (JSW) measurements made using standing CT (SCT) imaging.

Subjects and methods: This prospective two-visit study included 50 knees from 30 subjects (66% female; mean ± SD age 58.2 ± 11.3 years; BMI 29.1 ± 5.6 kg/m2; 38% KL grade 0-1). Tibiofemoral geometry was obtained from bilateral, approximately 20° fixed-flexed SCT images acquired at visits 2 weeks apart. For each compartment, the total joint area was defined as the area with a JSW <10 mm. The summary measurements of interest were the percentage of the total joint area with a JSW less than 0.5-mm thresholds between 2.0 and 5.0 mm in each tibiofemoral compartment. Test-retest reliability of the summary JSW measurements was assessed by intraclass correlation coefficients (ICC 2,1) for the percentage area engaged at each threshold of JSW and root-mean-square errors (RMSE) were calculated to assess reproducibility.

Results: The ICCs were excellent for each threshold assessed, ranging from 0.95 to 0.97 for the lateral and 0.90 to 0.97 for the medial compartment. RMSE ranged from 1.1 to 7.2% for the lateral and from 3.1 to 9.1% for the medial compartment, with better reproducibility at smaller JSW thresholds.

Conclusion: The knee joint positioning protocol used demonstrated high day-to-day reliability for SCT 3D tibiofemoral JSW summary measurements repeated 2 weeks apart. Low-dose SCT provides a great deal of information about the joint while maintaining high reliability, making it a suitable alternative to plain radiographs for evaluating JSW in people with knee OA.

Keywords: Computed tomography; Imaging; Knee osteoarthritis; Reliability.

MeSH terms

  • Female
  • Femur / diagnostic imaging
  • Humans
  • Imaging, Three-Dimensional
  • Male
  • Middle Aged
  • Osteoarthritis, Knee / diagnostic imaging*
  • Prospective Studies
  • Radiographic Image Interpretation, Computer-Assisted
  • Reproducibility of Results
  • Tibia / diagnostic imaging
  • Tomography, X-Ray Computed / instrumentation*