In one sentence, describe what the following article is about:

For the first 2 days after your injury, you should sleep with your back upright. Try sleeping in a reclining chair or propping yourself up on pillows in bed. Lie back in a reclined position with your shoulders propped up and supported. If you have an adjustable reclining bed, move the headrest up to a reclining position to sleep. Sleep on your unaffected shoulder, not on your injured shoulder. The pillow between your legs will help keep your body aligned properly as you sleep. You might also hug a pillow in your arms. Put the pillow under your arm to raise the arm and alleviate some of the pressure on your rotator cuff. This can help ease your rotator cuff pain as you sleep. You can use a regular pillow. These positions may cause more discomfort. Even if these are your normal sleep positions, try starting out in a different position.

Summary:
Sleep sitting up when you are first injured. Stick a pillow between your legs if you sleep on your side. Prop a pillow under the arm on the affected side when on your back. Avoid sleeping on the affected side or on your stomach.