Which is the best method to determine the patellar height in children and adolescents?

Patellar height is associated with various clinical syndromes. We asked which of three methods was the most appropriate for measuring patellar height for different age groups in terms of applicability, validity, and reliability. We evaluated 108 children and adolescents with available MR images and lateral knee radiographs using Insall-Salvati (IS), Blackburne-Peel, and Koshino-Sugimoto (KS) methods. Subjects were divided equally into three age groups (A, 5-10.9 years; B, 11-12.9 years; C, 13-18 years). The applicabilities of the three methods were evaluated using bony landmarks identified on lateral radiographs. For validation testing, standardized patellar tendon lengths determined by MRI were used as reference standards, and concurrent validity was analyzed by performing correlation tests. Intraobserver and interobserver reliability were determined using intraclass correlation coefficients. Of the three methods used to measure patellar height in this study, the IS appeared to be the most reliable and valid in patients older than 13 years with nearly complete ossification. Before this stage of ossification had been achieved, the KS was the only applicable and most reliable but less valid method in younger children.

Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.