For the causes of pain inside the arm, the specific reasons are as follows: First, upper limb trauma: such as muscle injury, fracture, dislocation, etc., can cause pain inside the arm, swelling, upper limb joint movement is limited, taking X-rays will find fracture lines as well as joint dislocation. Through early braking, rest, reset and fixation, the clinical symptoms can be quickly relieved. Second, cervical disc herniation, cervical spondylosis: when stimulating the nerves, it will lead to cause radioactive pain in one upper limb, bilateral upper limbs, and in serious cases, muscle atrophy and numbness in the upper limbs, while the patient has primary symptoms of the neck, such as pain and limited activity, and through MRI, lesions such as cervical disc herniation will be found. If there is pain inside the arm, it is important to diagnose and treat it early in order to get complete relief of clinical symptoms and avoid consequences such as serious muscle atrophy of the upper limbs.