I’ve just learned that my urinary incontinence is due to pelvic organ prolapse– what does this mean?

DEAR DOCTOR K: I'm a post-menopausal woman who suffers from urinary incontinence. I've just learned that my incontinence is due to pelvic organ prolapse. What does this mean? What is the treatment?
DEAR READER: Pelvic organ prolapse is a condition in which tissue from the uterus, bladder, urethra or rectum drops down into the vagina. As many as one in three middle-aged women have some degree of pelvic organ prolapse.