Endometriosis Back Pain: Why Your Lower Back Hurts and How to Tell It Apart

Why endometriosis hurts in the back

The uterosacral ligaments run from the back of the cervix to the sacrum, the triangular bone at the base of the spine. They are one of the most common sites of deep endometriosis. Lesions there, and in the pouch of Douglas behind the uterus, share nerve pathways with the lower back, so the brain locates the pain in the sacrum and lumbar region even though the source is pelvic.

Deep endometriosis can also irritate or infiltrate the hypogastric and sacral nerve plexuses that run along the back wall of the pelvis. When nerves are involved, pain can become burning or electric, spread to the buttock and hip, and persist between periods.

Inflammation itself plays a role. Endometriosis releases inflammatory mediators that sensitize nerves across the pelvis and lower back, so muscles of the pelvic floor and lower back tighten protectively and become a second source of pain.

How it feels: endometriosis back pain versus a "bad back"

• Timing: endometriosis back pain usually worsens in the days before and during a period, and may ease afterward. Mechanical back pain does not follow the cycle.
• Location: low and central, over the sacrum and tailbone, often felt deep rather than in the muscles on either side of the spine.
• Company: it rarely travels alone. Painful periods, pelvic pain, deep pain with sex, painful bowel movements or bladder symptoms usually accompany it.
• Triggers: sitting for long periods, bowel movements and intercourse can worsen it, while bending and lifting, the classic triggers of muscular back pain, often do not.
• Response to treatment: it may improve on hormonal therapy that suppresses the cycle, which muscular pain would not.

When back pain travels to the leg

Some women describe pain that runs from the lower back into the buttock and down the leg, sometimes with numbness or weakness, and sometimes only around menstruation. This "cyclical sciatica" is uncommon but important, because it can mean endometriosis is affecting the sacral plexus or sciatic nerve directly. It is covered in detail in our article on endometriosis and leg pain and warrants assessment by a surgeon experienced in pelvic nerve disease.

Other causes your doctor will consider

Not all back pain in a woman with endometriosis is endometriosis. Adenomyosis, fibroids, pelvic floor muscle dysfunction, sacroiliac joint problems and lumbar disc disease can all cause similar pain, and more than one can be present at once. The key question is whether the pain tracks the cycle. Keeping a daily record that notes both pain and cycle day usually answers it.

What helps

• Treating the endometriosis: hormonal therapy that suppresses menstruation often reduces cyclical back pain; excision surgery of uterosacral and rectovaginal disease addresses the source.
• Pelvic floor physical therapy: releases the protective muscle guarding that develops around chronic pelvic pain and is one of the most effective measures for back and pelvic pain together.
• Heat, anti-inflammatory medication and gentle movement around menstruation.
• For nerve-type pain, neuropathic pain medication and, in selected cases, nerve-sparing surgery.

What to tell your doctor

Describe where the pain sits, when in your cycle it is worst, what else hurts at the same time, and whether it reaches your buttock or leg. Bring a record covering at least two cycles. If you are being seen for back pain alone, mention your period pain and any pain with sex or bowel movements; those details are what redirect the evaluation from the spine to the pelvis.