Editorial Commentary: Radiographic Quantification of Patellar Alta May Reference Patellar Position Relative to the Tibia or to the Femur

Assessment of etiologic factors for the knee with patellar instability is important to construct an effective treatment strategy for each patient. Among the multiple risk factors for patellar instability, patella alta has been regarded as one of the principal morphologic abnormalities affecting bony constraint on excessive patellar motion. Although a number of radiographic measurement methods for patellar height have been proposed and tested for the reliability and diagnostic accuracy in the literature, consensus has not been reached on the optimal method of image assessment. The patella-posterior turning point of the distal femur (P-PTP) distance is an innovative indicator for quantifying patella alta. Conventional methods for quantifying patella alta measure the distance between the patella and the tibia. In contrast, P-PTP references the patellar height measurement to the femur. A challenge is that P-PTP requires imaging a supine patient in full knee extension.