Various parameters related to growth and maturity have been shown to be risk factors for scoliosis curve progression. We previously identified correlations between curve progression and radiographic parameters in clinical practice, but there is a lack of research.The aim of this study was to investigate and identify the radiographic parameters that are risk factors for rapid curve progression in Lenke 5 or 6 adolescent idiopathic scoliosis (AIS).A retrospective review of patients who were prospectively enrolled at the initiation of brace wear and followed through completion of bracing or surgery was performed. The inclusion criteria were as follows: a Lenke type 5 or 6 classification, Risser sign grade 0 or 1 at the initial outpatient examination, a follow-up period of 6 months including a minimum of 4 follow-ups, At each visit, the whole spine x-ray was completed, the following data were measured and collected: angle of the lumbar curve (LC), rotation of the apical vertebra (RAV) in the LC, deviation of the apical vertebra (DAV) in the lumbar curve, clavicle angle, L5 tilt angle (TA), body mass index, flexibility of the LC (FLC), and peak angle velocity (PAV). A binary logistic regression analysis was used to assess the contribution of each variable to PAV onset. The touch types for the determination of the lowest instrumented vertebra (LIV) were compared at both the PAV and final follow-up.Thirty-six AIS patients were recruited. The binary logistic regression model indicated that the following variable values significantly contributed to a high risk of PAV occurrence: LC 30 degrees (OR=6.153, 95%CI=1.683-22.488, P=.006), RAV III (OR=15.484, 95%CI=4.535-52.865, P<.001), DAV 40mm (OR=8.599, 95%CI=2.483-29.784, P<.001), and TA 10 degrees (OR=2.223, 95%CI=3.094-27.563, P<.001). The touch types for LIV determination changed in 12 of 36 patients, with at least 1 segment added as the LIV between the PAV and the final visit.LC 30 degrees, RAV III, DAV 40mm, and L5 TA10 degrees were radiographic parameters associated with an increased risk of curve progression in Lenke 5 and 6 AIS. The orthopedic surgery performed at the PAV is the ideal timing, and it will preserve 1 active segment than later surgery.Level of evidence was 4.