MCAO are a cornerstone technology for current and future telescopes (g.e. ELT). The synergy between high-resolution near-infrared imagers and MCAO systems is already leading the way for the characterisation of the stellar content and the structural properties of all of those systems in the Galaxy for which optical observations are almost totally useless. I will give an overview of the results recently achieved for highly obscured globular clusters in the Milky Way bulge thanks to the MCAO system GeMS at the Gemini South Telescope. These results clearly demonstrate that, once both the photometric and astrometric performances of these systems are fully constrained (in terms of variable PSF, geometric distortions), then high-quality proper motion measurements entirely based on ground-based AO observations can be performed. This is going to be one of the major achievements of the AO community in stellar clusters studies.