KING

Researchers in Italy looked at patients with mild knee arthritis over a period of six years.

SEATTLE - Could arthritis in the knees actually be a pre-cursor to a certain kind of cancer? 

A new study says what's happening below the waist could be affecting your lungs.

Researchers in Italy looked at patients with mild knee arthritis over a period of six years. The findings: Arthritis was the first warning sign of lung cancer.

Dr. Lecia Sequist, of Massachusetts General Hospital, says this isn't the first time lung cancer and arthritis have been linked.

"We don't fully understand exactly what happens between the lung cancer and the joint pain, but there's probably some type of hormone or inflammatory molecule that's released by the cancer that then irritates the bones or the joints in your body and causes it," she said.

In the study the number of patients diagnosed with lung cancer was small - just fewer than two percent - and they were heavy smokers.

"As far as drawing conclusions from this study, it was provocative, but small and early," Sequist said. "You have to remember that 99 percent of the patients that had knee pain did not have lung cancer."

But knee pain could be an early warning sign.

"This study brings further awareness to the fact that lung cancer is an important disease, it's often diagnosed too late, and we need better and more precise ways to find it early," Sequist said.

In those patients that did have lung cancer, as soon as the tumor was removed their knee pain disappeared.