Assessment of knee ossification timings: Development and validation of an ordinal scoring protocol for age estimation using medical imaging

· Reliable evaluation protocols is essential for skeletal maturity assessment. · An 11-site ordinal scoring system quantifies knee skeletal growth on 3D imaging. · Consistent intra- and- inter- observer agreement on CT and MRI. · Morphological knee sites are more variable than traditional epiphyses. Assessing skeletal maturity using epiphyseal and morphological features with modern, reliable evaluation protocols is crucial for human identification efforts and paediatric growth monitoring. This study aims to develop and validate a scoring system for knee skeletal development on post-mortem computed tomography (PMCT) and magnetic resonance imaging (MRI) acquired from Australian and New Mexican children. A protocol for the skeletal knee was developed on 30 PMCT and 30 T2-weighted MRI scans of subadults aged eight- to- 22 years. DICOM image stacks from a Brisbane children’s hospital and the New Mexico Decedent Image Database (NMDID) underwent multiplanar reconstruction and anatomical alignment. The protocol comprised a three- to- six stage scoring process at four epiphyseal fusion and seven maturity indicator sites. Three observers of varying experience levels assessed the images across three days, with reliability quantified using an intraclass correlation coefficient (ICC). The protocol demonstrated high reliability and consistency, with excellent intraobserver agreement for CT (ICC = 0.985 (95 % CI: 0.93-1.00)) and MRI (ICC = 0.979 (95 % CI: 0.85-1.00)). Mean inter-observer reliability measures were good for CT (ICC = 0.886 (95 % CI: 0.75-0.95)) and MRI (ICC = 0.852 (95 % CI: 0.68-0.95)). The tibial tubercle demonstrated the most variability and long-bone epiphyseal union the least This research presents a highly reproducible method for assessing skeletal development of the knee in subadults, aligned with modern imaging standards. The methodology will have application in forensic human identification, age confirmation and clinical growth assessment