Ischiofemoral impingement (IFI) causes posterior hip pain by impingement of the ischium and the lesser trochanter (LT) of the femur. Congenital or acquired narrowing of the ischiofemoral space results in compression or impingement of the quadratus femoris (QF) muscle, leading to edema, pain, and sometimes sciatic nerve irritation. Lesser trochanterplasty, ischioplasty, or both have been proposed as an effective treatment in cases that do not respond to conservative management. Our purpose was to show the gross anatomy of the deep gluteal space and the abnormal relationship between the LT and ischium, QF muscle and sciatic nerve, and the endoscopic decompression of IFI. We retrospectively reviewed 13 female patients (mean age, 40.2 years) with IFI who underwent endoscopic treatment with resection of the LT. Outcomes were assessed at a mean follow-up of 10 months. The mean modified Harris Hip Score went from 48.6 points to 82.8 points at final follow-up. The mean visual analog scale score for pain decreased from 9.3 to 2.53. Endoscopic lesser trochanterplasty was an effective treatment of patients with posterior hip pain and radiologic and clinical features of IFI.