Ask a PT Response: "There are quite a few muscles located at or around your sacrum (gluteus maximus, superior/inferior gemellus, piriformis, etc.). Was there an incident which resulted in your injury? Stretching, in itself, might not be sufficient to help with your condition if you have other issues going on such as postural, mechanical, imblances, tightness, weakness (other areas besides hip flexors), etc. It would probably be best if you consult with a PT so that he or she can conduct and evaluation to determine what is contributing to your condition. The PT will then be able to develop a plan of care based on the findings and your specific needs."