Knee Pain Is Linked to Lung Cancer

It’s a common worry — a strange, inexplicable symptom turns out to be the first sign of an undiagnosed cancer. Such tales are understandably frightening — after all, who doesn’t suffer arbitrary aches and pains, especially as we age? While these shouldn’t be reason to live in fear, research has found a connection between certain unusual symptoms and cancer. Fortunately, this is a rare occurrence, but nonetheless, important to be aware of.


In one study, rheumatologists reviewed the records of 296 patients who came to a medical center with a painful knee. In five of these patients—all of whom were middle-aged men with a history of heavy smoking — X-rays showed suspicious growths in their lungs. These men had a type of cancer called non-small-cell lung cancer, which surgeons removed…in all five cases, the knee pain went away after their lung cancer was successfully treated. These results led the authors to suggest that after doctors rule out more common causes for arthritis in a painful knee, a chest X-ray is a good idea — especially in people who have smoked heavily.

To learn more, we spoke with Maria Suarez-Almazor, MD, PhD, a rheumatologist at M.D. Anderson Cancer Center in Houston. She has an interest in what’s known as “paraneoplastic syndromes” in illness, where seemingly unrelated problems are caused by your body’s attempt to heal itself from other diseases. It turns out that sometimes a malignant tumor produces substances that damage tissues in your body, while at other times such symptoms can be the result of your immune system’s effort to fight the tumor, which inadvertently harms healthy tissues.

The study mentioned above is intriguing, she said, while also pointing out that only a tiny percentage of the patients with knee pain actually had cancer. Nonetheless, she agreed that if doctors can’t find any reason for pain in one knee, such as an orthopedic cause, it might be reasonable to suspect a paraneoplastic syndrome.

Dr. Suarez-Almazor said that there are other well-known and more common paraneoplastic syndromes that may lead a doctor to test for cancer more quickly. She listed some examples:

  • Lung cancer is commonly associated with a problem called hypertrophic osteoarthropathy, which as cancer progresses can involve pain in many joints and is marked by clubbing of the fingers, with fingertips growing round and bulbous.
  • An early symptom of acute lymphoblastic leukemia in children is joint pain — particularly in a knee, along with anemia. Arthritis can also be observed in acute myeloid leukemia in adults.
  • Muscle weakness along with a specific type of rash around the eyes is a sign of a condition called dermatomyositis, which can be associated with a variety of cancers including lung, ovarian, stomach, colorectal and non-Hodgkin’s lymphoma.

It’s rare that mysterious pain turns out to be caused by cancer — but people who have joint or other pain or rashes of unknown origin should see their doctor. Chances are the problem will be something else entirely or you’ll get a clean bill of health and whatever it is will resolve naturally. In any case, you’ll likely feel better after ruling out the worst-case scenario.