Exercises to strengthen the SI joint: building the support your pelvis is missing

If you have had sacroiliac pain for more than a few weeks, you have probably discovered something disheartening: the stretches help for an hour and then the ache comes back. That is not a failure on your part. It is a clue. An SI joint that keeps flaring is almost always a joint that is moving slightly too much on one side, and no amount of stretching will fix a stability problem. What fixes it — slowly, unglamorously, and reliably — is strength. Specifically, strength in the ring of muscles that compress the pelvis and hold the joint steady as you walk, climb and turn. This guide covers which muscles those are, the exercises that build them, and how to progress from the first pain-free bridge to genuinely robust single-leg control.

Key takeaway: You strengthen an SI joint by strengthening the muscles that compress it — gluteus maximus and medius, adductors, deep abdominals, multifidus and pelvic floor. Begin with symmetrical work (bridges, clams, adductor squeezes, dead bugs, bird dogs), progress load and tempo over several weeks, and add single-leg control last. Expect two to three months of consistent work for lasting change.

What muscles are weak with SI joint pain?

The sacroiliac joint is held stable by two things: the interlocking shape of its surfaces, and the muscles and ligaments that squeeze it together. Clinicians call the second mechanism force closure, and it is where exercise makes its difference. The muscles involved form slings that cross the pelvis from several directions:

• Gluteus maximus — the powerhouse at the back of the pelvis, working with the opposite latissimus dorsi across the back
• Gluteus medius and the deep hip rotators — the side of the hip, keeping the pelvis level on one leg
• Adductors — the inner thigh, closing the front of the pelvis
• Transversus abdominis and the obliques — the deep abdominal corset
• Multifidus — the small muscles beside the spine that fine-tune the sacrum
• Pelvic floor — the base of the cylinder, which co-contracts with the deep abdominals

Any of these can be weak or, just as often, late — present but not switching on in time to brace the joint before load arrives. That is why slow, controlled exercise with attention to what you feel is more useful than heavy lifting early on. If gluteal weakness is the dominant picture, my guide to glute strengthening exercises goes deeper on that muscle group alone.

Phase one: symmetrical foundation (weeks 1–3)

Every exercise here loads both sides of the pelvis evenly. Do them daily or on alternate days, 2 sets each, slowly, within a pain-free range.

• Glute bridge — feet hip-width, press evenly through both heels, lift until hips are in line with knees and shoulders. Hold 2 seconds. 2 x 10. Feel: the back of the hips, not the lower back or hamstrings.
• Clam — side-lying, knees bent, heels together. Top knee opens without the pelvis rolling back. 2 x 12 each side. Feel: the side of the hip, deep.
• Adductor squeeze — a cushion between the knees, lying or sitting. 8 gentle 5-second squeezes, breathing throughout.
• Dead bug — arms up, knees over hips. Lower opposite arm and leg slowly while the low back stays gently in contact with the mat. 2 x 8 each side.
• Bird dog — four-point kneeling, reach opposite arm and leg long, not high. Hold 3 seconds. 2 x 6 each side. Avoid: the pelvis tipping toward the lifted leg.
• Pelvic floor and deep abdominal connection — exhale, gently lift the pelvic floor and draw the lower belly in about 30 per cent. Inhale, release. 8 breaths.

If this looks like the basic routine from my SI joint pain exercises guide, it should — the first phase of strengthening and the last phase of calming overlap on purpose.

Phase two: load and control (weeks 3–6)

Once phase one feels easy and symmetrical, add resistance and challenge to the same patterns rather than reaching for new ones.

• Banded glute bridge — a resistance band around the thighs, press the knees gently outward against it as you lift. 3 x 10.
• Side-lying leg lift — top leg straight, slightly behind the line of the body, heel leading. 2 x 12 each side. Feel: the side of the hip again, now working through a longer lever.
• Side plank from the knees — hips stacked, lift the pelvis and hold 15 to 20 seconds. 3 holds each side. This is the best exercise I know for lateral pelvic control.
• Bridge with march — at the top of a bridge, lift one foot an inch off the floor without the pelvis dropping. 6 slow alternating lifts. This is your first, gentle taste of asymmetry.
• Hip hinge with a dowel — standing, hinge at the hips keeping the back neutral, sit the hips back. 2 x 10. Teaches the gluteals to take load in standing.

Phase three: single-leg control (weeks 6 and beyond)

This is the phase people skip — or, more often, jump to far too early. Single-leg work is the goal of SI joint strengthening, because walking, stairs and getting out of a car are all single-leg tasks. But it is only safe once the pelvis can stay level.

• Single-leg bridge — one foot on the floor, the other knee drawn toward the chest. Lift without the pelvis tipping. 2 x 8 each side.
• Step-up to a low step — press through the whole foot, pelvis level, no push-off from the back leg. 2 x 8 each side.
• Standing hip hitch — stand on one leg on a low step, let the free hip drop then lift it using the standing-side hip muscles. 10 slow reps each side.
• Split squat, short range — a modest split stance, lower a few inches only, pelvis square. 2 x 8 each side. Reintroduce the movements from SI joint pain exercises to avoid here, gradually.

Stop and drop back a phase if any exercise brings the familiar one-sided joint pain rather than muscular effort.

How I healed my SI joint dysfunction — the pattern that works

I am wary of “how I healed” stories because they imply a trick. There is no trick. But there is a pattern I see again and again in the people who stop having flares, and it is worth spelling out:

1. They stop stretching and cracking it. Relief from a big stretch or a self-manipulation is fleeting and often loosens the joint further.
2. They calm it for one to two weeks with gentle release, short walks, and a pillow between the knees at night.
3. They commit to two to three months of progressive stabilisation — the three phases above — rather than a week of enthusiasm.
4. They fix the everyday asymmetries: sitting to dress, alternating which hip carries the child, ditching the one-shoulder bag, uncrossing the legs.
5. They rebuild single-leg strength last, so that stairs, hills and lunges come back as evidence of recovery rather than a cause of relapse.

Pain that has been present for years may need a physiotherapist’s help alongside this, and anyone with leg numbness or weakness, bladder or bowel changes, or pain after a fall should be assessed before starting.

How the SI Joint Pain protocol helps

Sophie’s 8-Week SI Joint Pain Program is the three-phase progression above, written out week by week — 32 exercises that begin with symmetrical release and foundation work, add load and lateral control in the middle weeks, and finish with the single-leg stability that keeps the joint settled once the programme is over. It removes the guesswork about when you are ready to progress, which is the decision most people get wrong on their own.

This article is for informational purposes only and does not constitute medical advice. Low back and pelvic pain can have several causes; if your pain is severe, radiates down the leg, comes with numbness or weakness, or doesn’t improve, please consult a physiotherapist or doctor before continuing.