There are several possible causes of left inner thigh pain: first, femoral head necrosis, which can radiate to the inner thigh or the front side of the knee. Second, strain of the inner thigh muscles. If there is a history of obvious trauma or acute exercise, consider the pain caused by strain of the inner thigh muscles. Third, hip impingement syndrome, if the sciatic and femoral bones hit each other, it will lead to radiating pain in the inner thigh, then it is necessary to conduct an MRI of the hip joint for diagnosis and treatment. Fourthly, if there is a tumor or infection in the inner thigh, if there is an infection or tumor in the perineum or soft tissue in the root of the thigh, there will be pain in the inner thigh, and then a swelling or pressure pain can be touched, and the diagnosis should be made by the related nuclear magnetic examination.