Bone metastasis is more likely to be considered as leg pain in lung cancer. Bone scan can be done to clarify whether bone metastasis occurs and the severity of bone metastasis, and the treatment of bone metastasis is mainly to actively treat the primary lesion, bone cement to prevent paraplegia, radiotherapy to delay bone destruction and pain relief, together with zoledronic acid or disulfiramab and pain relief drugs. If the patient is not considered as bone metastasis, it is necessary to consider pulmonary osteoarthritis, which is mainly caused by lung cancer secreting certain special active substances, resulting in pain at joints.