Pelvic girdle pain (PGP) happens when the three joints of the pelvis stop moving evenly, making the whole structure less stable and painful. It most commonly develops during pregnancy, but it can also affect people who have never been pregnant. Understanding the specific causes helps you recognize what’s driving the pain and what you can do about it.
How the Pelvis Normally Works
Your pelvis is a ring of bone held together by three joints: two sacroiliac joints at the back (where the spine meets the pelvis) and the pubic symphysis at the front. These joints normally move only slightly, working together as a unit. Thick ligaments and deep stabilizing muscles keep everything aligned. PGP develops when something disrupts that coordination, whether it’s loosened ligaments, uneven movement, muscle weakness, or direct injury.
Hormonal Changes During Pregnancy
The most common trigger for PGP is pregnancy, and hormones play a central role. Your body produces a hormone called relaxin, which loosens the ligaments around the spine and pelvis to make room for a growing baby and prepare for delivery. This loosening is necessary, but it reduces the stiffness that normally holds the pelvic joints in place. When those joints become more mobile than usual, they can shift unevenly, and the surrounding muscles and nerves bear extra load they weren’t designed to handle.
Not everyone who produces relaxin develops PGP. The pain seems to arise when the degree of loosening outpaces the body’s ability to compensate with muscle support, or when one joint loosens more than the others, creating asymmetry.
Biomechanical Stress From a Changing Body
Hormones set the stage, but the physical demands of pregnancy push things further. As the baby grows, the extra weight shifts your center of gravity forward. You naturally adjust how you stand, sit, and walk to compensate, and those adjustments put new strain on the pelvic joints. The combination of heavier load and looser ligaments means the pelvis has to work harder with less structural support.
This is why PGP tends to worsen as pregnancy progresses. The pelvis faces increasing weight at precisely the time its ligaments are at their most relaxed. Activities that load one side of the pelvis more than the other, like climbing stairs, rolling over in bed, or standing on one leg, often become the most painful because they expose the uneven joint movement at the root of the problem.
Risk Factors That Increase Your Chances
A systematic review and meta-analysis identified five significant risk factors for developing pelvic girdle pain during or after pregnancy:
- Previous low back pain. A history of back problems before pregnancy is one of the strongest predictors, likely because the stabilizing muscles and joint mechanics are already compromised.
- Pre-pregnancy BMI over 25. Carrying extra weight before pregnancy adds to the load on pelvic joints from the start, leaving less margin before symptoms appear.
- PGP in a previous pregnancy. If you experienced pelvic girdle pain before, the joints and ligaments may be more vulnerable the next time around.
- Depression during pregnancy. Mental health and pain perception are closely linked. Depression can heighten pain sensitivity and reduce engagement in physical activity that supports pelvic stability.
- Heavy physical workload during pregnancy. Jobs or daily routines involving prolonged standing, lifting, or repetitive bending place sustained stress on an already vulnerable pelvis.
Having one or more of these risk factors doesn’t guarantee you’ll develop PGP, but it does increase the likelihood. The more risk factors present, the earlier symptoms tend to appear and the more severe they can become.
Causes Outside of Pregnancy
Pregnancy is the most recognized cause, but PGP also affects men and non-pregnant women. The pelvis contains muscles, nerves, organs like the bladder and intestines, and complex joint structures, and problems in any of these areas can produce pain in the pelvic girdle region.
Common non-pregnancy causes include trauma or fractures to the pelvic bones, which can destabilize the sacroiliac joints permanently if not properly rehabilitated. Nerve irritation or compression in the lower back or pelvis can refer pain into the pelvic girdle. Pelvic floor dysfunction, where the muscles at the base of the pelvis become too tight or too weak, can alter joint mechanics and create pain patterns that mimic classic PGP. Inflammatory joint conditions can also target the sacroiliac joints specifically, producing stiffness and pain that worsens with rest rather than activity.
Athletes and people with physically demanding jobs sometimes develop sacroiliac joint dysfunction from repetitive asymmetric loading, like running, kicking, or heavy lifting with rotation. The mechanism is similar to pregnancy-related PGP: uneven forces across the pelvic ring cause one joint to move differently from the others.
How PGP Is Identified
There is no single definitive test for pelvic girdle pain. Clinicians typically use a combination of physical provocation tests to pinpoint which joints are involved. The most relevant include the posterior pelvic pain provocation test (P4), which applies pressure through the thigh to stress the sacroiliac joint, and the FABER test, which moves the hip through flexion, abduction, and external rotation to reproduce pain. These hands-on assessments, combined with your description of where the pain is and what triggers it, are usually enough for a clear diagnosis.
Imaging like X-rays or MRI is rarely needed for straightforward PGP. It becomes more useful when a clinician suspects something else is going on, such as a fracture, inflammatory arthritis, or nerve compression, particularly in non-pregnant patients or when symptoms don’t follow typical patterns.
Why the Pain Persists After Delivery
Most pregnancy-related PGP resolves within a few months of delivery as hormone levels normalize and ligaments regain their stiffness. For some people, though, the pain lingers. The same risk factors that predict PGP during pregnancy, particularly a history of low back pain, higher BMI, and heavy workload, also predict persistent pain postpartum.
When PGP continues after pregnancy, it usually means the pelvic joints haven’t returned to coordinated movement, or the deep stabilizing muscles haven’t recovered enough strength to support the joints under normal daily loads. This is why targeted rehabilitation focused on the muscles around the pelvis and lower back is a core part of treatment, both during pregnancy and after. The joints themselves aren’t damaged in most cases. They just need the muscular support system around them to catch up.