Editorial Commentary: How High Is Too High? Understanding the Limitations of Measuring Patella Alta

Patellar height is a primary risk factor for patellar instability, reflecting the increase in knee flexion required before the patella can engage in the osteochondral constraint of the trochlea. From a surgical perspective, measurements of patella alta are factored into the equation of when we should consider performing distalizing tibial tuberosity osteotomy (TTO), which can change the nature of the surgery and recovery for patients. The addition of TTO increases the risk and recovery time when compared with a soft tissue procedure alone, and furthermore, the distalizing component of TTO can increase the rate of nonunion or delayed union by 3-fold when compared with nondistalizing TTO. Therefore, our ability to precisely measure patella alta and indicate distalizing TTO is paramount in safely and adequately addressing the symptoms of patellar instability. Although the search for the optimal imaging measurement technique continues, those who are using advanced imaging measurements to assess patella alta should exercise caution when interpreting such numbers and consider the context of the patient. By understanding the principles and limitations of each measurement and the influence of additional morphologic risk factors, we can better identify which patients would benefit from distalizing TTO in the management of patellar instability.