The main common causes of left upper arm lateral muscle pain are generally the following: a. When patients perform left upper limb muscle exercise, they accidentally fall and cause local soft tissue injury, which can cause painful symptoms in the left upper arm lateral muscle. This can be done by applying local ice to reduce tissue exudation, applying hot ointment pack externally after 24 hours, applying blood circulation and blood stasis cream externally, and taking oral medications such as swelling and pain and bruising pills to promote faster relief of the painful symptoms of the left upper arm lateral muscle. Second, the patient can cause laceration of the lateral muscles of the upper arm of the left arm during exercise due to the large amplitude, accompanied by the formation of local hematoma. It is necessary to improve the ultrasound examination, clarify the size and location of the hematoma, perform skin incision and subcutaneous tissue debridement and drainage as soon as possible, completely stop the bleeding of the wound, and add a bandage after the operation, in order to completely improve the symptoms of pain in the lateral muscle of the left upper arm.