Lateral thigh muscle depression piece of possible causes of trauma, muscle atrophy, tumors and so on. 1. Trauma: there is a clear history of trauma to the thigh, and the soft tissue of the thigh under the action of external force damages the muscle rupture, thus manifesting the symptoms of depression and pain of the lateral thigh muscle. 2. Muscle atrophy: if there is a lack of activity for a long time after the fracture of the lower limb or hemiplegia after the stroke, there is atrophy of the thigh muscle, which can be manifested as the depression of the outer thigh muscle, weakness and other symptoms. 3. Tumor: mostly seen in malignant tumors, tumor cells erode normal soft tissues, leading to destruction of thigh muscles, thus manifesting as lateral thigh muscle depression accompanied by pain, emaciation and other symptoms. The causes of thigh muscle depression are many, and may also be related to kidney disease, developmental abnormalities, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in a timely manner, to clarify the cause of the disease, and to carry out targeted treatment.