Joints are held together by muscles and ligaments. When joints are out of balance such as with sitting at a computer craning the neck forward, it creates a constant contraction in the muscles of the shoulders which cuts off their blood flow. This results in a burning sensation over time and a "crunchy" texture/sound when the muscles are rubbed. To avoid this, try rolling your shoulders every 30 minutes to give your muscles some oxygen - "their snack". They like a break and a reward as much as you do. And then they won't complain as much either. Also, while sitting, lean back in your chair and hold your head straight on top of your shoulders.
