  Plain radiography is the most common modality to assess the stage of
osteoarthritis. Our aims were to assess the relationship of radiography-based
bone density and texture between radiographs with minimal and clinical
post-processing, and to compare the differences in bone characteristics between
controls and subjects with knee osteoarthritis or medial tibial bone marrow
lesions (BMLs). Tibial bone density and texture was evaluated from radiographs
with both minimal and clinical post-processing in 109 subjects with and without
osteoarthritis. Bone texture was evaluated using fractal signature analysis.
Significant correlations (p<0.001) were found in all regions (between 0.94 and
0.97) for calibrated bone density between radiographs with minimal and clinical
post-processing. Correlations varied between 0.51 and 0.97 (p<0.001) for FD_Ver
texture variable and between -0.10 and 0.97 for FD_Hor. Bone density and
texture were different (p<0.05) between controls and subjects with
osteoarthritis or BMLs mainly in medial tibial regions. When classifying
healthy and osteoarthritic subjects using a machine learning-based elastic net
model with bone characteristics, area under the receiver operating
characteristics (ROCAUC) curve was 0.77. For classifying controls and subjects
with BMLs, ROCAUC was 0.85. In conclusion, differences in bone density and
texture can be assessed from knee radiographs when using minimal
post-processing.
