<s>[INST] I just had a mri done and I suffer with a lot of lower back pain. My legs go out from under me its just that bad. My report said "there is a nonspecific region of adnormal marrow signal seen anteriorly within the upper sacum demonstrating homogeneous low signal on T1-weighted images and homogeneous high signal on T2- weighted images measuring 3.6cm transverse x 1.6cm craniocaudad x 2.3cm AP dimension. What does this mean? [/INST] Hi, welcome to HCM.     Such abnormal marrow signal in sacrum needs furhter evaluation. There must be something detail in report. It could be just a age related marrow conversion or any bony pathology. We need images to comment  exactly.     You need to visit your orthopaedician and radiologist again for examination of this. Dedicated scan for sacrum may be needed again.Hope I have answered your query.Regards. </s>