A hard lump in the muscle is often caused by the following reasons: first, lipoma, lipoma can also grow in the muscle, you need to go to the hospital to check ultrasound or CT, etc. for clarification. If the fatty tumor does not increase rapidly and is not painful, there is no need to worry too much and regular observation is sufficient. If there is a significant abnormality, it needs to be removed surgically to prevent malignant transformation into liposarcoma. Second, it may be caused by leiomyosarcoma, which is a malignant disease. It is necessary to go to the hospital as soon as possible to improve the relevant examination and perform the enlargement of the swelling to remove it, and other treatments may be needed at a later stage. Third, it may be caused by the formation of blood clots, which needs to be clarified by ultrasound. If it is a thrombus, anticoagulation, volume expansion and removal of aggregates should be carried out, and strenuous activities should be reduced and local pressure should not be applied as much as possible. Fourth, some patients are caused by foreign body, which also need to be removed surgically.