The SI joints, where the base of the spine meets the pelvis on each side, can trigger muscle spasms when they become irritated or unstable. Unlike the hip, an SI joint has no deep socket and depends on ligaments and muscles to hold it steady.1Maywell Health. Why SI Joint Pain Keeps Coming Back and How to Stop the Cycle When the joint is in trouble, the surrounding muscles are pulled into a job they aren’t built for, and spasm is a common result. The relationship also runs both ways, which is why the pain and tightness often return together.
Why An Irritated SI Joint Makes Muscles Spasm
When the joint’s ligaments are strained or loose, the muscles around the pelvis and spine try to take over the job of holding it steady.2Erik Dalton Blog. The Sacroiliac Struggle But those muscles are designed to move the body, not to brace a joint for hours.3Erik Dalton Blog. The Sacroiliac Struggle So they stay contracted, a protective reflex known as guarding.4Erik Dalton Blog. The Sacroiliac Struggle Along with wear or arthritis, this can leave the joint and nearby tissues stiff.5Midwest Pain And Wellness. What Is Sacroiliac Joint Dysfunction and How to Treat It
Muscles that stay tight squeeze their own blood supply.6Erik Dalton Blog. The Sacroiliac Struggle Waste products and inflammatory chemicals then build up and set off pain nerves.7Erik Dalton Blog. The Sacroiliac Struggle Strained pelvic muscles can spasm around the SI joint, giving a painful “locked” or “fixed” feeling.8Erik Dalton Blog. The Sacroiliac Struggle The joint can end up held in an off-centre position by the very muscles trying to protect it.9Erik Dalton Blog. The Sacroiliac Struggle
Day to day, this usually feels like a deep ache or grabbing tightness on one side of the low back or buttock, near the dimple above the buttock. It is often worse after standing up from sitting, rolling over in bed, or climbing stairs. Some people feel as if the pelvis is stuck, or one hip is “off.” The tightness may ease with gentle movement and come back with long sitting.
That locked feeling differs from an ordinary cramp. A cramp comes on suddenly, is intense, and usually lets go within a minute or so. SI-related tightness is a lower-grade, lingering grip that builds over hours or days. Because the muscle is reacting to the joint, it tends to be tied to certain positions or movements rather than striking at random.
“Off-centre” doesn’t usually mean a bone has slipped out of place, since the SI joint moves only a few millimetres normally. What people feel is more likely uneven muscle pull and a joint that is moving or loading differently than usual. That’s why self-cracking or self-manipulation doesn’t reliably fix it.
The spasm itself isn’t the root problem. Relaxing the muscle alone may bring short relief, but the trigger remains, and lasting relief usually means restoring support so the muscles can stop guarding.
Guarding is partly a reflex driven by the nervous system, so you can’t simply decide to relax these muscles. They respond to signals from an irritated joint and its ligaments. After days of guarding, the muscles can feel sore and bruised to the touch, even though the original trigger was the joint rather than an injury to the muscle.
Which Muscles Are Usually Involved
The large buttock muscle, the glute, tends to be weaker on the painful side in people with SI joint problems.10PubMed Central. STRENGTHENING THE GLUTEUS MAXIMUS IN SUBJECTS WITH SACROILIAC DYSFUNCTION In one comparison, about two-thirds of people with SI joint dysfunction had weak glute muscles, versus about one-third of people with other low back pain.11PubMed Central. The relationship between hamstring length and gluteal muscle strength in individuals with sacroiliac joint dysfunction Those with weak glutes also tended to have tighter hamstrings.12PubMed Central. The relationship between hamstring length and gluteal muscle strength in individuals with sacroiliac joint dysfunction When the glutes underperform, other muscles tighten to compensate, which sets up spasm.
The hamstrings and glutes both help extend the hip, so when the glutes do less, the hamstrings are often recruited to do more. A muscle working beyond its usual role tends to stay tense, which can show up as tightness at the back of the thigh. Hamstrings attach near the sitting bone and pull on the pelvis, so persistent tightness there can add strain to the SI joint.
The glutes are also stabilizers, not just power muscles. They keep the pelvis level every time you stand on one leg, which is half of every step. When the glute on one side is weak, the pelvis can drop or shift with each step, adding repeated stress to the SI joint.
A spasm in the piriformis, a deep buttock muscle, can strain the SI joint, and a strained joint can trigger piriformis spasm.13PubMed Central. Piriformis syndrome as an overlooked cause of pain in a patient with axial spondyloarthritis: a case report The two are hard to separate. Piriformis pain sits deeper in the middle of the buttock and can send tingling down the leg, while SI pain sits higher, near the bony dimple at the back of the pelvis. Pain when sitting on a hard chair is common to both, and since they often happen together, a clinician may treat both.
Pelvic floor muscles normally help stiffen and steady the SI joint under load.14Carolina Pelvic Health. Sacroiliac (SI Joint) Pain: The Pelvic Floor Muscles and Gluteal Strength are the Key When they are too tight or too weak, they can disturb pelvic mechanics and add to pain.15Carolina Pelvic Health. Sacroiliac (SI Joint) Pain: The Pelvic Floor Muscles and Gluteal Strength are the Key Pelvic floor spasm has been linked to the base of the spine shifting toward the tighter side, and a shortened psoas with a blocked SI joint.16Journal of Orthopaedic Medicine. Pelvic Muscles Influence the Sacroiliac Joint Pain with sitting, sex, or bowel movements can point to pelvic floor tension. A pelvic floor physical therapist can check this internally or externally. It’s common after childbirth but happens in men too.
The psoas is a deep muscle running from the lower spine through the pelvis to the top of the thigh, so it pulls on both the spine and the hip. Long hours of sitting keep it shortened, which can leave it tight when you stand up. A tight psoas can tilt the pelvis forward and change how load passes through the SI joint, one reason hip-front tightness and back-of-pelvis pain can show up together.
Why The Pain And Spasms Keep Coming Back
Once movement is limited, a cycle of pain, spasm and stiffness can keep itself going and become long-lasting muscle pain.17Erik Dalton Blog. The Sacroiliac Struggle Weak glutes and core muscles leave the joint unsupported and contribute to recurring pain.18Maywell Health. Why SI Joint Pain Keeps Coming Back and How to Stop the Cycle
The back of the body works as one chain. The glute on one side links through connective tissue to the back muscle on the opposite side, and this crossing sling helps press the SI joint closed and stable with each step. When this link weakens, tension can show up farther along the chain.
Walking changes too. People with one-sided SI joint problems tend to extend the hip less and put less weight through the painful side.19PubMed Central / Elsevier. Individuals with sacroiliac joint dysfunction display asymmetrical gait and a depressed synergy between muscles providing sacroiliac joint force closure when walking The glute on that side works less in step with the opposite back muscle.20PubMed Central / Elsevier. Individuals with sacroiliac joint dysfunction display asymmetrical gait and a depressed synergy between muscles providing sacroiliac joint force closure when walking Runners with SI pain tend to land with a straighter knee and their foot further ahead of the body.21PubMed Central. Running gait biomechanics in female runners with sacroiliac joint pain
Everyday habits keep the loop going: standing with weight on one leg, sitting cross-legged or for long stretches, and resting completely, which lets support muscles weaken further. A short rest during a sharp flare can be reasonable, but staying still for days costs the joint its support. Stiffness builds too, so the first steps after rest can hurt more than before. The usual path is to return to gentle movement early and rebuild gradually, rather than waiting until the pain is completely gone.
A flare can seem to come from nowhere. It often follows a small trigger such as a long drive, a day of standing, or a new workout, because the joint’s support is already marginal. Noticing which activities or durations tend to come before a flare lets you adjust early, before the spasm takes hold.
What Helps The Spasms And The Joint
Across controlled trials, exercise reduced both pain and disability for SI joint dysfunction.22PubMed. A systematic review and meta-analysis of randomized controlled trials on the effect of various therapeutic interventions on sacroiliac joint dysfunction Muscle energy technique, where you push gently against a therapist’s resistance and then stretch, also reduced pain.23PubMed. A systematic review and meta-analysis of randomized controlled trials on the effect of various therapeutic interventions on sacroiliac joint dysfunction The brief contraction lets tight muscles around the joint relax and lengthen afterward.24PubMed Central. Efficacy of Mulligan Mobilization, Maitland Mobilization, High-Velocity Thrust, and Muscle Energy Technique for Pain, Disability, and Center-of-Gravity Displacement in Patients With Sacroiliac Joint Dysfunction: Protocol for a Randomized Controlled Trial Joint mobilization reduced pain, but taping did not clearly help.25PubMed. A systematic review and meta-analysis of randomized controlled trials on the effect of various therapeutic interventions on sacroiliac joint dysfunction In athletes, a quick manipulation and muscle energy technique both cleared most positive test findings, with manipulation doing slightly better.26PubMed Central. Effectiveness of the Muscle Energy Technique versus Osteopathic Manipulation in the Treatment of Sacroiliac Joint Dysfunction in Athletes
In a muscle energy session, the therapist positions your leg or pelvis so a particular tight muscle is gently stretched, then asks you to push lightly against their hand for several seconds. You then relax, and the therapist moves you a little further into the stretch, often repeating the cycle a few times. The effort should be light and painless. Pushing hard can make the muscle tighter.
The exercise evidence needs a realistic reading. The trials used different programs, so no single routine has been proven best. Benefits usually build over weeks of steady practice rather than after one session. If the pain isn’t improving after several weeks of consistent effort, that is a reason to be reassessed rather than to push harder.
At home, glute bridges and side-lying leg raises build the muscles that support the joint. Start with a few gentle repetitions and stop if sharp pain appears. Keep both legs moving evenly, and avoid big one-sided lunges early on. A physical therapist can tailor the plan and check your form.
During a spasm, heat helps tight muscles, while ice can calm a fresh flare. Gentle knee-to-chest or figure-four stretches may ease the grip. Short walks often help more than lying still, and sleeping with a pillow between the knees keeps the pelvis level.
A muscle relaxant such as cyclobenzaprine may ease spasms that come with an inflamed SI joint.27Mayo Clinic. Sacroiliitis – Diagnosis and treatment Muscle relaxants are mainly used for sudden, acute flares.28PubMed Central. Sacroiliac Joint Pain: Causes and Treatment Options They are prescription medicines and often cause drowsiness, so they’re meant for short use. Avoid alcohol and driving until you know how they affect you.
Dry needling targets tight knots in the glutes and low back muscles to ease spasm and pain.29Wildflower Physical Therapy & Wellness. Unlocking Relief: How to Manage Sacroiliac Pain and Dysfunction Its evidence comes mostly from clinics rather than large trials.
For severe pain that doesn’t respond to other care, fusing the joint greatly reduces its movement and can give lasting relief.30Pain Physician. Subchondral Bone Changes Following Sacroiliac Joint Arthrodesis – A Morpho-mechanical Assessment of Surgical Treatment of the Painful Joint That makes fusion a last step, not a spasm treatment.
How Doctors Confirm The SI Joint Is The Source
Clinicians use hands-on moves that stress the SI joint to see if they reproduce your pain.31SI-BONE. Sacroiliac Joint Provocative Tests In the figure-four test, you lie down with one ankle crossed over the other knee while the examiner presses the bent knee down.32Back Muscle Solutions. 3 Tests to Tell You If Your Back Pain is Caused By SI In the thigh thrust, your hip and knee are bent to 90 degrees and pressure is pushed down through the thigh.33Back Muscle Solutions. 3 Tests to Tell You If Your Back Pain is Caused By SI SI joint dysfunction is usually considered when at least three of five tests are positive, including the thigh thrust or compression test.34PainTEQ. SI Joint Provocative Tests for Diagnosing SI Joint Dysfunction | PainTEQ | LINQ Procedure for SI Joint Dysfunction
A positive result isn’t simply discomfort or a stretch but a reproduction of the pain you recognize from daily life. Say clearly whether it matches your usual pain, since that match is what makes the test meaningful.
No single pain-provoking exam test is reliable enough alone. Hip and lumbar spine problems can also hurt during some of the moves, so a cluster of positives is more convincing than one.
Many people with SI joint problems also feel pain down the leg, which can be mistaken for a pinched nerve.35PubMed Central. Radiculopathy with concomitant sacroiliac dysfunction and lumbosacral degenerative disease: illustrative case Groin pain is reported by up to nearly half.36PubMed Central. Radiculopathy with concomitant sacroiliac dysfunction and lumbosacral degenerative disease: illustrative case Leg pain alone doesn’t rule the SI joint in or out.
Tell your clinician exactly where the pain starts and where it spreads, which movements trigger spasms, and whether you’ve had a fall, a pregnancy, or a change in activity.
Some signs point elsewhere. Numbness or leg weakness needs prompt checking, and loss of bladder or bowel control or numbness around the groin needs urgent care. Long-lasting morning stiffness in a young adult can be one clue to inflammatory arthritis. Fever with back pain needs medical review.
SI Joint Pain And Spasms In Pregnancy
During pregnancy the body makes more relaxin, a hormone that loosens pelvic ligaments for birth.37hingehealth. Sacroiliac (SI) Joint Pain in Pregnancy: Tips and Exercises The pelvic joints become less stable as a result.38Elite HP. Sacroiliac Joint Pain During Pregnancy Explained The muscles around the SI joint then pick up more of the load, which fits the guarding pattern behind spasms.
Pain tends to be worse with activities that load one leg at a time, such as climbing stairs, turning over in bed, or getting dressed. Spasm and tightness can appear when the muscles tire from the extra work of steadying the joint.
Pain can begin early, when hormone levels rise, well before the growing belly adds weight. As pregnancy advances, changing posture and added weight put more demand on the already looser joint. For many people symptoms improve after birth, though some continue and benefit from targeted rehabilitation.
A pelvic support belt can add stability. Worn low across the hips, it gently compresses the pelvis, doing part of the job the loosened ligaments can’t. It’s most useful during activities that bring on pain, such as walking or standing for long periods, rather than all day, and it supports you while you build strength rather than replacing movement and exercise.
Small habits help too. Keep your knees together when getting out of bed or a car, and sit to dress rather than standing on one leg. After birth, pelvic floor and glute work helps restore support. See your midwife or doctor if pain makes walking hard.