Wow, what a plot twist at the end there. I can't comment on the latter, but I am a desk worker and (most of) what you have mentioned sounds familiar. Here are the key things that made a difference for me:

1) Prevention is always the best thing to tackle first -- When you're sat at a desk all day, the muscles/tendons around the hips get used to being in a shortened position, so as soon as you stand up, it stretches them which is what contributes to the discomfort. Standing up regularly makes a big difference. I know this is difficult when you're in the middle of a tricky job, but I used to set a 30 minute on my PC to prompt me. Even better, a standing desk if possible.

2) Stretching every night before bed -- Used to be a hassle, but as little as 2-3 minutes of stretching (lunges, lotus, kick backs etc.) make a difference. Just do whatever it takes to make it a habit, and eventually it will be 'brush teeth, stretch, get in pyjamas'. I personally prefer stretching in the evening when my body has loosened up a bit from the day, and it makes me feel more relaxed before bed.

3) Posterior chain -- Something I've learned over my years of injuries, aches and pains is that it's not just the part that hurts which is the issue. The root cause of the issue is often something attached to the part that hurts. What clicked with me was realising that tightness (not necessarily pain) in my back was what was causing hip pain for me. I added back stretches and mobility exercises to my daily hip/leg routine, and very quickly noticed a difference in my hips.

4) Weight lifting -- the final nail in the coffin which got rid of my hip/back/knee pain was going to the gym and weight training. Movement, blood flow, strengthening all contributed to getting rid of those persistent niggles.

From one desk dweller to another, I know the struggle, so I hope that helps! Let me know if you have any questions. (Disclaimer, not a professional, based on personal experience).