We exploit the increased sensitivity of the recently installed adaptive optics SOUL at the LBT to obtain new high-spatial-resolution near-infrared images of the massive young stellar object IRAS20126+4104 and its outflow. We used both broad-band (Ks, K') and narrow-band (Br{gamma}, H_2)) observations from a number of near-infrared cameras (UKIRT/UFTI, SUBARU/CIAO, TNG/NICS, LBT/PISCES, and LBT/LUCI1) to derive maps of the continuum and the H_2_ emission in the 2.12 micron line. Three sets of images, obtained with adaptive optics systems (CIAO, in 2003; FLAO, in 2012; SOUL, in 2020), allowed us to derive the proper motions of a large number of H_2_ knots along the jet. Photometry from all images was used to study the jet variability.