Bone-cartilage interfaces: An imaging perspective

In medical imaging, the bone-cartilage interface refers to the anatomical and radiological boundary between the subchondral bone and overlying hyaline cartilage. Direct visualization of this interface is challenging for multiple reasons, but advances have been made. This perspective focuses on the visualization and clinical relevance of the cartilage-bone interface as visualized by magnetic resonance imaging (MRI), discusses the concept of the meniscal-osteo-chondral unit, introduces cartilage classification systems in the context of this interface and briefly addresses the role of computed tomography (CT) arthrography.

Recent developments in MRI technology including optimization of ultrashort echo time (TE) sequences allow for direct visualization of the osteo-chondral junction. Despite these advances, the clinical relevance of these imaging findings remains incompletely understood to date. The concept of the osteo-chondral-meniscal unit reflects the close anatomical and functional interrelation between different joint tissues at a local level and has implications for disease progression. Cumulative tissue damage on a subregional joint level substantially increases risk for cartilage damage progression. Cartilage delaminations are typically a result of shear forces and are clinically relevant as these may not be fully appreciated during arthroscopy but may require surgical treatment. The International Cartilage Regeneration & Joint Preservation Society (ICRS) cartilage classification system includes damage of the osteochondral interface while most other systems do not include subchondral bone changes. CT arthrography remains the imaging reference standard for assessing surface morphology and detecting subtle surface defects. Despite its strengths, it is likely underutilized in both clinical trials and routine clinical practice.

The cartilage-bone interface is best comprehensively evaluated using advanced MRI techniques. The close interrelation between different joint tissues on a subregional joint level must be considered when considering individualized treatment strategies.