The Spatial Order of Physeal Maturation in the Normal Human Knee Using Magnetic Resonance Imaging

Background: The spatial order of physeal maturation around the distal tibia has been shown to place adolescent patients at risk for certain transitional injuries, such as Tillaux or triplane fractures. Less is known about physeal maturation around the knee. The purpose of this study was to establish the spatial order of physeal maturation in the normal human knee using magnetic resonance imaging (MRI). Methods: We retrospectively collected all knee MRI scans from patients presenting to our institution from January 2004 to January 2014. Patients who were suspected on the basis of clinical or radiographic findings of having abnormal knee physeal development or injury were excluded. We then applied a previously described MRI staging system of knee physeal maturation to the MRI scans of the remaining patients at 8 defined knee locations. Associations between the stage of maturation and mean chronological age were then evaluated across the 8 knee locations. Interrater and intrarater reliabilities were assessed. Results: A total of 165 knee MRI scans (from 98 boys, 67 girls) met the inclusion criteria. Significant differences were found between each stage of physeal maturation and the mean chronological ages at all 8 knee locations for both boys and girls (each, P<0.001). Interestingly, within each stage of physeal maturation, no significant difference was found in the mean chronological ages at any of the 8 knee locations, suggesting that physeal development occurs uniformly in the normal human knee for both boys and girls. Interrater and intrarater reliability were nearly perfect at all locations. Conclusions: The spatial order of physeal maturation in the normal human knee was uniform across 8 knee locations for both boys and girls. This uniformity may help to explain why transitional injuries do not follow a recognizable pattern in the knee. Furthermore, the uniformity aids with surgical decision making, because minimal growth modulation or disturbance is likely when early physeal closure is present in a portion of the physis. Level of Evidence: Level III.