I have a long track record of RSIs and other injuries that have affected my ability to sit and work at a desk, so I'm unfortunately very well-qualified to tell

I have a long track record of RSIs and other injuries that have affected my ability to sit and work at a desk, so I'm unfortunately very well-qualified to tell you what's worked for me. Despite it all, I still happily work a full-time desk job with the help of these coping mechanisms. First, standing desk. You don't need to stand all day; in fact I don't recommend it. You just need to switch it up at least once an hour so you're never sitting for more than an hour. Find excuses to walk around, too -- a 5-minute stroll around the block is great for thinking. Second, have you had an ergonomic evaluation? There may be something about your setup that's all wrong, and a professional can help you correct it. Finally, consider going to physical therapy for your leg pain. A good physical therapist can identify posture problems that contribute to your pain, and give you exercises to correct it.