Age-related variability in elbow joint capsule thickness in asymptomatic children and adults.

The purpose of this study was to establish normal ultrasonographic measurements for elbow joint capsule thickness in children. Transverse posterior ultrasonographic images of 53 elbow joints in asymptomatic patients were digitized, and off-line measurements were performed and compared to the corresponding scale present on each image to yield a reliable measurement in millimeters. Joint capsule thickness measurements regressed with age. Significant differences existed between three age groups. Joint capsule thickness is under 1 mm in children 1 month to 2 years of age, increased significantly to just over 1 mm from 2 to 15 years of age, and approached 2 mm in thickness at and after 15 years of age.