If your grandmother says her aching knees are proof rain is coming, you'd better take in the outside laundry.

A group of Pennsylvania doctors say our joints know a lot about the weather.

Unfortunately, they sometimes tell us through pain.

Just ask Lillian Johnson.

She says for her, when there's rain there's pain.

And what's more, she's as good as any meteorologist when it comes to forecasting.

Lillian says she knows when it's going to rain because of arthritis in her knees.

She says the tell-tale signs will begin about two days before the moisture drops.

Orthopedic surgeon Dr. Javad Parvizi says joints have sensory nerves called Baro-Receptors which respond to changes in atmospheric pressure.

Like when the barometer moves from dry to rain.

Arthritic joints feel it more because they have less cartilage, which cushions the joint.

It can happen in any load bearing joint, but it's most common in hips, hands, elbows, shoulders and knees.

The doctor says keeping joints warm, massage therapy, and applying pain killing creams and ointments can help.

There is one other option.

Lillian says as much as she hates the rain, she's not tempted to move.