Is tibial tuberosity–trochlear groove distance an appropriate measure for the identification of knees with patellar instability?

Purpose Tibial tuberosity–trochlear groove distance (TT–TG) has been regarded as a useful tool for establishing therapeutic choices for patellar instability. Recently, it has been shown that TT–TG negatively correlated with the quadriceps angle, suggesting that if used individually, neither provide a valid measure of instability. This study aimed to compare TT–TG distance between both knees in patients with unilateral instability to assess whether this measurement is a decisive element in the management decisions for patellar instability.