Strengthening the sacroiliac (SI) joint means building up the muscles that compress and stabilize it, since the joint itself can’t be strengthened like a muscle. The SI joint sits where your spine meets your pelvis, and it relies heavily on surrounding muscles to stay stable during movement. When those muscles are weak or poorly coordinated, the joint becomes vulnerable to excessive motion and pain. An estimated 15 to 30 percent of chronic lower back pain cases involve the SI joint, making it one of the most common and overlooked sources of pain in the lower back and buttock region.
The good news: a targeted exercise program can meaningfully improve SI joint stability within 6 to 12 weeks, and most people notice reduced pain well before that. The key is understanding which muscles matter most and training them in the right order.
How the SI Joint Stays Stable
The SI joint has two layers of stability. The first is its physical shape. The sacrum is wider at the top than the bottom, so it wedges between the two hip bones like a keystone in an arch. The bone surfaces themselves have interlocking ridges and grooves that create the highest friction of any joint in the body, resisting the shearing forces that would otherwise pull it apart.
The second layer is active muscle control, sometimes called “force closure.” This is where strengthening matters. Muscles, ligaments, and connective tissue generate compressive forces across the joint, essentially squeezing it together to keep it locked in place. This compression is adjustable: your body increases it automatically when loads get heavier, like during walking, lifting, or standing on one leg. When the muscles responsible for this compression are weak or poorly timed, the joint loses its self-bracing ability and becomes painful.
The Muscles That Matter Most
Several muscle groups work together to compress and stabilize the SI joint. Training them as a system produces better results than focusing on any single muscle.
Deep core muscles. The transversus abdominis (the deepest abdominal layer), lumbar multifidus (small muscles along the lower spine), and pelvic floor muscles all fire in anticipation of movement. They activate before you take a step, reach overhead, or shift your weight. Because they sit close to the joint’s center of rotation, they can exert strong compressive force even with relatively small contractions. Research has shown that voluntary contraction of the deep abdominal wall reduces laxity at the SI joint.
Gluteal muscles. The gluteus maximus connects directly to the sacrotuberous ligament and the thoracolumbar fascia, two structures that cross the SI joint. When the glute max contracts, it tensions these structures and increases compression. The gluteus medius, which sits on the outer hip, is a primary pelvic stabilizer during single-leg activities like walking and climbing stairs. Research from the University of North Dakota found that gluteus medius weakness is present in a significant number of people with SI joint dysfunction, and that recruiting it improved lower extremity stability.
Pelvic floor muscles. These muscles resist lateral movement of the hip bones, helping keep the sacrum centered between them. There is a clear connection between pelvic floor function and SI joint stability, particularly in women. When the pelvic floor is dysfunctional, the body compensates with outer abdominal muscles, which can actually worsen pelvic mechanics.
Foundational Exercises to Start With
Begin with low-load exercises that teach your stabilizing muscles to activate properly before progressing to heavier work. Quality of movement matters more than intensity in the first few weeks.
Glute bridge. Lie on your back with both knees bent and feet flat on the floor. Lift your hips until your body forms a straight line from shoulders to knees. Hold for about 6 seconds, then slowly lower. Repeat 8 to 12 times. This targets the gluteus maximus and hamstrings while keeping the SI joint in a neutral, supported position. Once this feels easy, progress to single-leg bridges by extending one leg while lifting.
Bird-dog. Start on your hands and knees. Tighten your belly muscles by drawing your navel toward your spine (keep breathing normally). Raise one arm straight in front of you while extending the opposite leg behind you. Hold for 6 seconds, return to the start, and switch sides. This exercise trains the deep stabilizers of the spine and pelvis to work together across the body, which mirrors how the SI joint is loaded during walking.
Clamshell. Lie on your side with knees bent and feet together. Keeping your feet touching, raise your top knee as high as you can without letting your hips roll backward. Hold for 6 seconds and slowly lower. Repeat 8 to 12 times on each side. This isolates the gluteus medius, which is frequently weak in people with SI joint problems.
Single knee-to-chest stretch. Lie on your back with knees bent and feet flat. Clasp your hands under one knee and pull it gently toward your chest while keeping your other foot on the floor and your lower back pressed flat. Hold for 15 to 30 seconds. Repeat 2 to 4 times per leg. This mobilizes the hip and gently stretches the muscles around the pelvis without stressing the joint.
Progressing Your Program
Once you can perform the foundational exercises without pain for two to three weeks, you can add challenge. The goal is to increase the demand on your stabilizers while keeping the SI joint in safe positions.
Side-lying hip abduction (lifting the top leg straight up while lying on your side) increases gluteus medius load beyond what the clamshell provides. Pallof presses, where you resist a band pulling you into rotation while standing, train your obliques and deep core to resist the twisting forces that destabilize the SI joint. Dead bugs, performed lying on your back while slowly extending opposite arms and legs, challenge core stability without spinal compression.
For people who want to return to barbell training, front-loaded squats (goblet squats with a dumbbell or kettlebell) tend to be better tolerated than back squats because they encourage a more upright torso and reduce shearing at the pelvis. Start light and increase gradually, paying attention to any return of symptoms.
Exercises and Activities to Avoid
Certain movements create shearing or asymmetric forces across the SI joint that can worsen instability and pain, especially early in a strengthening program.
- Heavy deep squats compress the spine and stress the SI joint, particularly if your form breaks down under load.
- Full sit-ups pull on the lower spine and can aggravate SI joint pain. Planks and dead bugs are safer core alternatives.
- Twisting plyometrics like twist jumps or rotational throws generate rapid, intense torque through the pelvis.
- Running and jumping create jarring impact forces with every footstrike or landing. These can be reintroduced later but are risky during the early strengthening phase.
- Leg press machines lock your back into a fixed position while placing heavy force through the pelvis, which can strain the SI joint under resistance.
- High-intensity interval training and boot camps combine many of these problematic movements in rapid succession, leaving little room to control form.
The common thread is high impact, heavy asymmetric loading, or rapid rotation. As your stability improves over several months, you can cautiously reintroduce some of these activities if they’re important to you.
How Long Results Take
Most people begin to notice reduced pain and improved stability within 4 to 6 weeks of consistent training, though this varies with the severity of dysfunction. Meaningful muscle strength gains typically require 8 to 12 weeks. If you’ve had SI joint pain for months or years, expect the process to take longer, as the stabilizing muscles may have significantly weakened from disuse.
Consistency matters more than intensity. Performing your exercises 3 to 5 times per week at moderate effort will produce better results than occasional intense sessions. The deep stabilizers respond especially well to frequent, low-load training because their primary role is sustained postural control, not peak force production.
When Exercises Alone Aren’t Enough
If you’ve been consistent with a strengthening program for 8 to 12 weeks and still have significant pain, it’s worth getting a proper assessment. Clinicians diagnose SI joint dysfunction using a set of five provocation tests: if three or more of them reproduce your pain, the SI joint is the likely source. This combination has about 94% sensitivity, meaning it catches the vast majority of true SI joint problems. In uncertain cases, an image-guided anesthetic injection into the joint can confirm the diagnosis.
For people whose pain doesn’t respond to physical rehabilitation, other options include joint injections for pain management, prolotherapy to tighten loose ligaments, or in more severe cases, SI joint fusion surgery. Recovery from fusion typically takes three to four months before returning to full activity. But the majority of people with SI joint dysfunction improve substantially with targeted strengthening alone, provided they’re training the right muscles with enough consistency and patience.