A stuck ring can simply be the result of wearing a ring that's too small. It can also be caused from arthritis of joints, which can happen as your body changes over the years. This can cause the joints and/or tissue to swell, which prevents you from removing your ring.
Here's how to get a ring off safely:
Slip the thread or floss under the stuck ring with the bulk of it toward the fingertip.
Beginning at the top of the ring, snuggly wrap the finger with the thread/floss around and around, compressing the finger, all the way up and over the knuckle.
With the end that was under the ring, begin to unwrap the thread or floss with the ring sliding over the knuckle as you go.
*If all else fails, cut the ring off with a ring cutter found in jewelry stores, fire departments and emergency rooms.