Typical symptoms of lung cancer are cough, blood in sputum, chest pain, shortness of breath, etc. However, about half of the lung cancer patients show symptoms outside the lungs at the beginning. In clinical practice, we often encounter “arthritis” and “frozen shoulder” that have not been cured for a long time, and after the temporary effect of symptomatic treatment, they quickly recur, and even the symptoms are worsened. If it is lung cancer, why is there no lung symptom but joint pain instead? Lung cancer is not easily detected in early stage because when the tumor does not touch the trachea, there will be no coughing symptom; when it does not invade the pleura, there will be no chest pain; when it does not infiltrate the blood vessels, there will be no hemoptysis. As for why lung cancer causes joint pain, some literature reports suggest that cancer cells will cause abnormal secretion of growth hormone in the process of proliferation and differentiation. A large amount of growth hormone will stimulate abnormal proliferation of bone joints and invade large joints such as knee, ankle and wrist, resulting in symptoms such as swelling and pain. According to the literature, the incidence of lung cancer combined with arthralgia in the elderly is about 10% to 20%. When symptoms such as cough with blood in sputum, chest pain and pain fixed in one place appear, of course, prompt lung X-ray and CT examination should be done. If the symptoms of arthritis such as bone pain are symmetrical and the effect of treatment with general anti-inflammatory painkillers is not obvious, it is also necessary to consider the possibility of lung cancer and have relevant examinations in time to avoid misdiagnosis. Bone metastasis of advanced lung cancer can also cause joint pain. In addition, joint pain, back and leg pain, etc. may also be caused by bone metastasis of advanced lung cancer. This is the case of a patient whom the reporter contacted in the interview. This year, 70-year-old Uncle Zhao repeatedly visited several hospitals in the city for back and leg pain, and finally, after a rehabilitation treatment, he suddenly couldn’t walk, and later, after CT examination, he found that a tumor had grown in his pelvis. The tumor was not the primary lesion, but the root of the disease was actually lung cancer, and the tumor in the pelvic bone was actually a bone metastasis of lung cancer. This patient did not have symptoms such as coughing and coughing blood during the whole process of medical treatment, but when he was finally diagnosed with lung cancer, it was already at an advanced stage, and the patient barely lasted less than 2 months before he passed away. It is understood that bone metastasis is a common complication in the late stage of lung cancer, with ribs and spine as the most frequent sites, followed by pelvis, limbs and skull. Pain is the first symptom of lung cancer bone metastasis, and about 75% of lung cancer bone metastasis patients will experience pain.