There are several possible causes for the pain in the medial aspect of the left thigh in men: First, diseases of the femoral head. When there is aseptic necrosis of the femoral head, pain in the medial aspect of the thigh can occur, often accompanied by significant pain when the hip is weighted, and then MRI or CT examination of the femoral head should be performed for early diagnosis and treatment. Second, impingement syndrome, when the hip joint has impingement syndrome, it can also appear the pain of the inner thigh root, then MRI and X-ray examination of the hip joint should be carried out for diagnosis and treatment. Third, inflammation of lymph nodes, there are lymph nodes in the groin of the thigh root, when there is inflammation of lymph nodes, there can also be pain in the inner thigh root, then the relevant examination and related blood tests should be conducted to make a diagnosis. Fourth, tumor, if there is a tumor in the inner thigh muscle or soft tissue, it can also appear the pain in the inner thigh root, then the relevant soft tissue nuclear magnetic examination should be conducted to make the diagnosis.