Some general rules for good sitting are:
- Always try to have your hip position higher than your knee joint position.
- Make sure your feet can be placed flat on the ground.
- When you lean forward bend at your hip joints not at your lower spine
- Try to keep the natural curves through your spine - car seats are often the worst for this!!
- Have your desk height such that you reduce the need to slump
- Set your keyboards and monitors in a position to maintain this good posture - if you can't touch type then learn!!
- Try to take regular breaks form sitting and stretch your hip flexors and upper spine.
Choice of chair is relevant. The main criteria is that it can adjust up/down to suit your height and can tilt forward to aid hip/knee alignment. Having a back on the chair does not have great relevance unless it is fully supportive of good posture.
If there is pain associated with sitting and pain persists after making all the correct postural adjustments then it may be that the pelvic and low back stabilising muscles are inactive and lack endurance. Your Physiotherapist and Sports Doctor can assess the function of your stabilising muscle and head you down the pathway of retraining those muscles.