Basal thumb joint osteoarthritis is a common condition, which can be very invalidating and can cause a lot of pain. Until now, there are many different techniques to treat basal thumb joint osteoarthritis. Because there is no clear consensus which technique is best, we are evaluating the different options before and after treatment. With this research, we try to find the best fitted treatment per patient with basal thumb joint osteoarthritis. To expand the research in different hospitals, we have a collaboration with the UMC Utrecht, the Jeroen Bosch Ziekenhuis in ’s Hertogenbosch and the Erasmus MC in Rotterdam.