AbstractThis study was to analyse the risk factors of unstable patella and the incidence of tissue damage (TD) with magnetic resonance imaging (MRI) image under the modified particle swarm optimization (MPSO). In this study, 45 patients with patella instability who visited hospital from 1 November 2018 to 28 September 2020 were selected as the experimental group (group E), and 45 volunteers with healthy knee joints were recruited as the control group (group C). MRI images under MPSO were to evaluate the four groups of related indicators (trochlear groove angle, trochlear groove depth, trochlear surface ratios, and Insall‐Salvati index) of unstable patella in the two groups and count the incidence of TD caused by unstable patella. Comparison of four indicators revealed that there was an obvious difference in the data of the two groups. The abnormal rate of patients with unstable patella in the group E was much higher than that of the group C, and the difference was statistical (p < 0.05). The incidences of trochlea dysplasia and high patella accounted for 88.9% and 57.8% in group E and accounted for 4.4% and 3.2% in the group C, respectively, showing statistically obvious differences (p < 0.05). The incidence of patella cartilage TD, thigh cartilage TD, lateral meniscus TD, medial meniscus TD, patella medial retinaculum TD, patella lateral retinaculum TD, patellar ligament damage, and joint effusions were 14.5%, 11.45%, 50.38%, 49.62%, 10.69%, 16.03%, 9.16%, and 79.39%, respectively in the patients with unstable patella in the group E. In short, trochlear dysplasia and high patella were risk factors for unstable patella, and unstable patella was one of the risk factors for multiple TDs of the knee joint. This study provided a new research basis for the early treatment of unstable patella.