Improving comparability of microCT assessment and reporting of subchondral bone in mouse models of osteoarthritis

Subchondral bone is a critical component of the osteochondral unit, but its translation from histology to quantitative imaging studies using micro-computed tomography (microCT) remains inconsistent. Definitions diverge on how far the subchondral region extends from the articular surface, how volumes of interest (VOIs) are defined, how subchondral bone plate is separated from subchondral trabecular bone, and whether articular calcified cartilage is included in the analysis. In murine models of osteoarthritis, where tissue dimensions approach the imaging voxel size, these issues are further magnified.

This review synthesises anatomical, histological, and imaging perspectives; catalogues how recent microCT studies define and segment compartments.

MicroCT cannot reliably distinguish articular calcified cartilage from subchondral bone plate at typical laboratory resolutions; most studies implicitly integrate articular calcified cartilage into subchondral bone plate or adopt workarounds (fixed VOIs in weight-bearing zones, data-driven thresholds, or manual delineation). The resulting divergence affects key outcomes (e.g. subchondral bone plate thickness/volume, tissue mineral density).

We offer re--ations for reporting (i) imaging resolution; (ii) VOI boundaries relative to anatomical landmarks, including how intercondylar regions are handled; (iii) definition, method, and parameters used to separate subchondral bone plate and subchondral trabecular bone; (iv) relevant metrics for each compartment; (v) how articular calcified cartilage was handled, using broader terms such as "calcified tissue layer" or "subchondral mineralised plate" when separation is not feasible; and (vi) a clear schematic of the selected VOI and compartments. Transparent, anatomy-anchored reporting will improve interpretability between murine studies and facilitate translation of algorithms and findings.