Many women experience some degree of lower back pain before or around the beginning of their menstrual period. This pain is often part of their normal period or premenstrual syndrome (PMS). Less commonly, it is caused by a disorder such as endometriosis. The type of pain, when it occurs and associated symptoms may provide clues about the cause.
Mild pain around the time of a period is common. This pain -- called dysmenorrhea -- is caused by hormones called prostaglandins, which stimulate the uterus to contract. These contractions produce intermittent, cramping pain. Dysmenorrhea is usually felt in the lower part of the abdomen, but it may also occur in the lower back, hips or thighs. Contractions begin before the onset of menstrual bleeding, so back pain due to dysmenorrhea can begin hours to as many as 2 days before a period. It usually resolves by the second or third day of the period. When severe, dysmenorrhea may be accompanied by fatigue, nausea and diarrhea.
When dysmenorrhea occurs as a natural part of a menstrual cycle, it is called primary dysmenorrhea. This type of dysmenorrhea usually begins soon after a girl starts menstruating and improves with age. Secondary dysmenorrhea generally appears later in life and is the result of another medical disorder, such as endometriosis or noncancerous growths of the uterus called fibroids.
PMS is a set of symptoms that occurs before the start of a menstrual period. When lower back pain occurs with PMS, it tends to be constant, not cramping. Other PMS symptoms may include tension or anxiety, depression, crying spells, mood swings, difficulty sleeping, poor concentration, headaches, fatigue, fluid accumulation, abdominal bloating, lower abdominal pain and breast tenderness. PMS symptoms, including back pain, often begin several days before a period and typically subside within the first few hours after the period starts.
The exact cause of PMS is unknown, but hormonal changes in the days leading up to a period likely play a key role. Back pain during PMS may be caused by an increase in a hormone called relaxin, which causes ligaments to relax. When back ligaments relax, the lower back loses some of its natural support, which may result in pain. Fluid accumulation and abdominal bloating may also contribute to lower back pain.
Endometriosis is a condition in which tissue from the inner lining of the uterus -- called the endometrium -- grows in another location. The endometrial tissue may appear on the outer surface of the uterus or nearby organs, such as the ovaries, bladder or bowel. Researchers aren't sure exactly why endometriosis occurs, but one theory is that during a period, menstrual blood containing endometrial cells backs up into the fallopian tubes and then spills into the abdomen.
During a woman's menstrual cycle, hormones cause the endometrial tissue to swell and bleed as if it were in the uterus. This bleeding can irritate the surrounding area, causing pain. Symptoms depend to a large extent on where the endometrial tissue is located. Pain in the lower back or lower abdomen is common. This pain usually occurs before or during a period -- producing secondary dysmenorrhea -- but it may persist between periods as well. Endometriosis may also cause pain or bleeding during or after intercourse, pain with urination or bowel movements, difficulty becoming pregnant, excessively heavy periods or vaginal bleeding between periods.
Seeking Medical Attention
See your doctor if back pain before your period interferes with your life or is not controlled by simple measures, such as over-the-counter pain medications or a heating pad. Also seek medical attention if there is a significant change from your regular pattern of pain or if you have symptoms of possible endometriosis. Seek prompt medical care if you have severe pain in your back or abdomen, your period is very heavy or you feel lightheaded or extremely weak.
Reviewed and revised by Mary D. Daley, MD.
- Merck Manual Professional Version: Premenstrual Syndrome (PMS)
- Merck Manual Professional Version: Endometriosis
- American Family Physician: Primary Dysmenorrhea
- American Family Physician: Evaluation and Treatment of Endometriosis
- Cleveland Clinic: Premenstrual Dysphoric Disorder (PMDD)
- The American College of Obstetricians and Gynecologists: Dysmenorrhea -- Painful Periods