Musculoskeletal ultrasound (MSUS) is an important tool for evaluating disease activity, therapeutic progress, and remission status of rheumatic diseases in children. Knowledge of age-related normal findings is essential when interpreting pathological findings such as those seen in juvenile idiopathic arthritis. To evaluate normal findings of the knee joint, we recorded age-related stages of musculoskeletal development in the knee of 435 healthy children between 1 and 18 years of age using high-resolution B-mode MSUS. We determined approximate age- and sex-related norms for the suprapatellar recess size, ossified patella size, and distal femoral intercondylar cartilage thickness. In almost all age-groups, over 64 % of children had visible fluid accumulation in the suprapatellar recess. Significant correlations were found between chronological age and the suprapatellar recess size and ossified patella length (p < 0.05). An age-dependent decrease in intercondylar cartilage thickness of the distal femoral epiphysis was found in children between 10 and 18 years of age. High-resolution B-mode MSUS is an excellent tool for assessing joint and skeletal development in children. Our reference data can be used to discriminate better between normal physiological findings and pathological abnormalities.
Keywords: Cartilage thickness; Knee; Musculoskeletal ultrasound; Ossification; Patella size; Suprapatellar recess.