This is a good stretching exercise if you have problems with arthritis.
Stand in relaxed position with your feet shoulder width apart.
Your back is straight, chest is up and shoulders are relaxed.
Place your arms to the sides of your body.
Lean to the side and try to reach your knee and return to the center.
Repeat the same motion to the other side and you will feel a stretch at the opposite side.
Be careful not to over bent.