tried the cold water thing

Started ending my shower with two minutes of cold water because someone at the running club mentioned it for joint pain. I have done it six times now. The first three were unpleasant in a way that felt productive, which I am aware sounds odd. My knees were noticeably less stiff on the two mornings after, then back to normal by day five. My mood was slightly better on those days but I had also slept more, so I cannot separate the causes. I am not stopping it. I am also not telling anyone it works because I do not know that yet.