To determine whether leg pain is caused by lung cancer, first of all, CT examination of lungs should be improved in time, that is, to clarify whether there is corresponding mass or occupying lesion in lungs through CT examination of lungs. Bone scan of the whole body should be done to clarify whether there is bone metastasis, because lung cancer will only cause corresponding leg pain symptoms if there is bone metastasis, and lung cancer itself will not cause leg pain. Symptoms of lung cancer are mainly cough, blood in sputum or chest pain, and other metastatic symptoms will only appear in middle and late stages when distant metastasis occurs. If leg pain is caused by lung cancer, it is usually caused by bone metastasis. Therefore, the first thing to do is to find out whether there is bone metastasis or not, so bone scan and CT examination of lung should be done.