Knee Pain and Lung Cancer: What's the Link?

Knee pain and lung cancer may not be what you commonly think of when joint pain symptoms occur, but knee pain can be a sign of lung cancer in very rare instances.

It's common to see a healthcare provider for knee pain, but you may want to discuss a cancer screening even if you don’t have a cough, weight loss, or “typical” signs of lung cancer. That's especially true for people at high risk of lung cancer because of smoking, genetics, environmental exposure, or even their male gender at birth.

This article explains some of the reasons for why knee pain may be a sign of lung cancer and how this diagnosis is made. It also briefly presents a few of the treatment options for lung cancer.

How is Knee Pain Related to Lung Cancer?

Knee pain and lung cancer may be linked in a few ways. The pain may occur if a tumor metastasizes, or spreads, to connective tissue areas, or it may be the result of unusual complications associated with lung cancer. This is how lung cancer can spread to the knee.

Metastases

Lung cancer is most commonly associated with metastases to the brain, lymph nodes, liver, and adrenal glands, but it can spread almost anywhere, including the synovial tissue. This is a type of connective tissue in the protective membranes surrounding the body’s joints.

When lung cancer metastasizes to these areas of the body, it is usually a lung adenocarcinoma. The joints most likely to be affected are the knees.

When the knee is impacted in this way, symptoms may include:

• Pain
• Swelling
• Decreased ability to stand
• Impaired ability to straighten the knee

Surgery to remove the entire tumor is usually the first course of treatment for cancer in the synovial tissue. Chemotherapy may also be recommended to increase the chances of eliminating all of the malignant cancer cells.

Paraneoplastic Syndromes

People with lung, ovarian, lymphatic, or breast cancer are at risk of developing paraneoplastic syndrome, a rare complication in which cancerous tumors cause organ or tissue damage that can trigger the production or release of hormones or other chemicals. Paraneoplastic syndromes affect approximately 10% of all people with lung cancer.

Rheumatic and neurologic tissue are among the most commonly affected by paraneoplastic syndromes related to lung cancer.

Hypertrophic Pulmonary Osteoarthropathy (HPOA)

This rare type of paraneoplastic syndrome can be the first sign of knee pain linked to lung cancer. Substances secreted by a lung tumor or made by the body in response to a lung tumor can cause swelling and inflammation.

Signs of HPOA (sometimes called HOA) may include:

• Painful inflammation and swelling in the knees, as well as the ankles, wrists, and elbows
• Clubbing (swelling of the ends of the finger)
• Koilonychia (spoon-shaped nails)

Once the tumor is removed, the knee pain or other symptoms related to HOA should improve. Treatment may also include nonsteroidal anti-inflammatory drugs (NSAIDs) or bisphosphonates, medications typically prescribed to treat osteoporosis.

Knee Pain as a Symptom of Lung Cancer

Both monoarthritis (pain in one joint) and polyarthritis (pain in multiple joints) have been identified as possible signs of lung cancer. Sometimes, these symptoms can be misdiagnosed.

The connection between knee pain and lung cancer can easily be missed because the rate of arthritis problems occurring with lung cancer is very low. For example:

• Arthritis symptoms due to a paraneoplastic syndrome occur in approximately 0.24% of lung cancer patients.
• HPOA incidents among lung cancer patients range from 0.72% to 17%.
• Researchers have only reported 48 cases of synovial metastasis, and only a fraction of those incidents are related to knee pain.

If you have lung cancer, your knee pain is more likely to be related to other causes and is rarely a symptom of your lung cancer.

Diagnosis

If you have lung cancer and knee pain, your healthcare provider will first look for the obvious causes of joint disease or injury.

The connection between knee pain and lung cancer may only be found if your pain persists or if your discomfort spreads to other joints.

If you haven't been diagnosed with lung cancer, you might get tested for any of the following reasons:

• You have signs of a paraneoplastic syndrome, such as clubbing
• X-rays of your knee are concerning
• Your joint pain doesn't respond to treatment

Computed tomography (CT) scan of the chest and a biopsy of the lung may be ordered to confirm a cancer diagnosis.

Treatment Options

If lung cancer is identified as the cause of your knee pain, your treatment will focus on removing or reducing the size of your tumor via surgery, chemotherapy, and/or radiation.

The type of surgery and the course of chemotherapy and radiation will depend on where the tumor is located, its size, and its type.

Your healthcare provider may also prescribe steroids, high-dose intravenous immunoglobulin, or irradiation.

A Word From Verywell

Lung cancer incidence and treatment have changed over the years. Today, young never-smokers, notably women, are developing the disease more often. Vague symptoms may occur before classic symptoms.

If your knee hurts or other unusual health symptoms arise, talk with your healthcare provider. It's better to get checked out and determine the root cause as soon as possible.