HOUSTON -- If you're one of the thousands of women suffering from an achy, sore back, you may be inadvertently causing the problem yourself -- by wearing the wrong bra, Local 2 reported Thursday.

The proper fit can make all the difference, according to experts, and can alleviate back pain.

An estimated 75 percent of women are wearing the wrong bra, according to industry experts.

Doctors say knowledge is key and women should not make their purchase on looks alone.

"Women do want something that is very feminine and pretty and makes them feel good about themselves," said Barbara Nelson, with Top Drawer Lingerie.

But fit should come first.

"If it's wrong, as in too big, it won't support the breasts. If it is too tight, it will actually cause a restriction of the lymphatic system as well as the vascular system," said Dr. Eric Tondera, a chiropractor.

The wrong fit can cause upper back pain and even headaches.

"It causes stress on the back with the muscles," Tondera said.

There are signs that a bra is not the right size.

"You will see red marks where the bra straps go, which you should not have," Tondera said.

Jana Barrett knows what that's like.

"I didn't know that that could be such a big sign," Barrett said.

The most common mistake is the bra is too small, according to Tondera.

Here are other signs of a bad-fitting bra.

The breast overflows out of the cup.
The bra band rides up on the back
The center of the bra, or the underwire, does not lie flat on the chest.
The material is wrinkled on your breasts. It should stretch firmly for proper support.

Sales consultant Mary Kathryn Langhmer helps shoppers make the right choice.

To get the right measurement, measure around the chest first, right under the breasts.

"The most important for support is the band, and you don't want that too loose," she said.

For cup size, measure around your chest at mid-breast. Subtract that from your first number and get a difference in inches.

A 1 inch difference equals an A cup.
A 2 inch difference equals a B cup.
A 3 inch difference equals a C cup .

"By having support around the base is a lot better than having to use your shoulders where (it) all rides up," Langhmer said. "It's very wise to be fitted at least once a year because our bodies change."

"I think it's like any other clothing. You need to try it on," Barrett said.