I'm not a big fan of the advice by internet, because to solve your problem a PT would need to assess you. However, as a bit of general advice, look up intu-flow on utube. It's free to watch the basic videos. Try it for 2-3 weeks. As a guess, focus on the movements around your ankle and knees, but make sure you do the movements for the neck, hip and back and your arms if you use your upper limbs for work. It looks scary at first but can be done in 10mins a day.
The main principle to observe is to do the movements short of any resistance and with smooth control. If you can only move your ankle 1cm before getting any slight sensation of tightness in the muscles then work within that 1cm of the free and easy range. Let me know if you notice any change from doing this.