The importance of proper posture!
The most common issue I see with my clients who have desk-jobs is a postural misalignment called anterior pelvic tilt. The back, hip flexors/psoas, hamstrings and quads become tight. The glutes and abdominals become inactive. The forward slumping also over extends the shoulder and back muscles and places pressure on the neck.
All of this tightness causes muscular imbalances, tilting your pelvis forward and rounding your lower back. The results are back pain, knee pain (particularly knee cap misalignment), hip pain and shoulder/neck pain.
It is important to prevent or improve misalignment through the proper strengthening and flexibility routine.
Understand ergonomics and improve your efficiency in the workplace.