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Updated: Jun 5, 2026
Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography
Published on: March 12, 2021
Impact of quantified knee positioning on the measurement of minimal joint space width using statistical shape models:
Eva A Bax1, H Chien Nguyen1,2, Roel J H Custers1
1Department of Orthopaedic Surgery, University Medical Center Utrecht, the Netherlands.
Objective:
Correlations between minimum joint space width (mJSW) and MRI-based cartilage thickness are strong in cross-sectional analyses and moderate in longitudinal analyses, possibly due to knee rotation and flexion. This study investigates the effect of knee positioning during radiographic acquisition on the difference between mJSW and MRI-based cartilage thickness.
Methods:
Radiographic mJSW from the index knee was determined from baseline (265 patients) and 24-month follow-up (165 patients) on fixed-flexion radiographs from IMI-APPROACH (multicenter OA study) patients using automated software. Statistical Shape Models were used to quantify knee rotation and flexion on radiographs. Cartilage thickness was assessed by manual segmentation from MRI. Differences between mJSW (radiographs) and cartilage thickness (MRI) were assessed at baseline and follow-up. Multivariable linear regression was used to evaluate the impact of knee flexion and rotation on the difference between mJSW and cartilage thickness.
Results:
In cross-sectional analysis, differences between X-ray and MRI were significantly influenced by knee rotation (β = -0.18, P < 0.001). Longitudinal change in differences between X-ray and MRI were associated with changes in knee flexion (β = 0.19, P=0.002). Increases of one standard deviation in internal rotation and extension at follow-up resulted in a 0.2 mm false surrogate measurement of cartilage changes on radiographs.
Conclusion:
Quantified knee positioning significantly affects differences between mJSW measured on radiographs and MRI-based cartilage thickness. The longitudinal analyses revealed that knee flexion was related to these differences, while knee rotation was only related to cross-sectional differences. These findings highlight the importance of knee positioning during radiographic acquisition in contributing to false surrogate measurement of cartilage status and cartilage change.
