What causes sacroiliac dysfunction?
The sacroiliac joint sits where the base of your spine meets the pelvis, and it is built to move very little while transferring everything your legs do up into your trunk. When it stops sharing that load evenly, the surrounding tissue gets irritated and the pain parks itself on one side, low and deep. It is often mistaken for a disc, for the hip, or for sciatica, because it can refer into the buttock and the back of the thigh. The examination separates them.
Hormonal changes loosen the pelvic ligaments to make room for the baby, and the sacroiliac joints lose some of their passive stability. The muscles have to take over, and if they are not ready, one side starts to hurt. This is common, it is treatable, and it does not resolve on its own just because the pregnancy ended. Pelvic health is a stated specialty here, and the work is specific rather than general core exercise.
When a hip is stiff, the pelvis borrows movement from the joint above it. Every time you reach the end of the hip's range, the sacroiliac joint gives up a little more motion to cover for it. That is why treating only the painful side often fails. We test the hips first, restore what they have lost with hands-on work, and the SI joint stops being asked to do the hip's job.
Coming down hard on one leg, missing a step, or landing on the tailbone can shove the joint into a position it does not settle back from. The pain arrives quickly and stays on one side. Manual therapy and specific manipulation restore the position and the movement, then strengthening keeps it there, because a joint that got shifted once will shift again if nothing around it changed.
Habits load the pelvis unevenly. Standing with your weight parked on one leg, sitting on a wallet, driving with the seat twisted, sleeping curled with the top knee dropped forward. Any of these, repeated daily, asks one sacroiliac joint to carry more than its share. Part of your plan is finding the loaded habit and changing it, because treatment that ends at the clinic door has to compete with the rest of your day.
The sacroiliac joint is held by muscle as much as by ligament. When the glutes and the deep abdominal wall are weak or poorly timed, the joint takes the force directly. Generic core work rarely fixes this, because the problem is usually timing and endurance rather than raw strength. We test which muscle is late, train it specifically, then load it in the positions that hurt you now.
