The sacroiliac joint is one of the most misunderstood pain generators in the lower back and pelvis region. It is the joint that connects the sacrum (the triangular bone at the base of the spine) to the ilium (the large pelvic bone on each side), and it is the structure through which the compressive forces of the upper body are transmitted to the lower extremities during every step, every lift, and every athletic movement.
Sacroiliac joint pain is common, affecting an estimated 15 to 30 percent of people with lower back pain, yet it is frequently diagnosed late because its symptoms overlap significantly with lumbar disc pathology, hip pathology, and piriformis syndrome. When the SI joint is the primary pain source, the treatment approach differs meaningfully from other lower back pain causes, and strengthening the muscles that stabilise the joint is a primary component of conservative management.
This guide covers the specific muscles that stabilise the SI joint, why targeted strengthening produces better outcomes than generic core training for SI joint problems, and a complete structured exercise programme.
Important note: Sacroiliac joint pain has several potential causes, some of which require specific medical management. This guide is written for informational purposes and does not replace a clinical assessment. If SI joint pain is severe, accompanied by neurological symptoms, or not responding to conservative management, seek assessment from a doctor or physiotherapist.
The Sacroiliac Joint: Anatomy Relevant to Strengthening
The sacroiliac joint is a synovial joint with a small but important range of motion (typically 2 to 4 degrees of rotation and 1 to 2 millimetres of translation). Unlike most joints, the SI joint depends primarily on passive stability from its strong surrounding ligaments and on muscular stability from the surrounding muscles rather than on the joint’s bony architecture for support.
The force closure mechanism:
The sacroiliac joint achieves stability through a mechanism called force closure: the muscles surrounding the joint compress it from multiple directions simultaneously, creating a self-locking mechanism that resists the shear forces that would otherwise cause painful joint movement. When the muscles providing force closure are insufficient, the joint relies excessively on its passive ligamentous structures, which produces the characteristic SI joint pain that worsens with prolonged sitting, standing, and activities that load the pelvis asymmetrically.
The muscles most important for SI joint force closure:
Gluteus maximus: The largest contributor to SI joint stability through its connection via the thoracolumbar fascia. The gluteus maximus and its fascia create a posterior compressive force across the SI joint that is the most powerful active stabilisation mechanism available. Research consistently identifies gluteus maximus weakness as a primary contributing factor to SI joint dysfunction.
Biceps femoris (hamstring): The long head of the biceps femoris has a direct attachment to the sacrotuberous ligament, one of the primary ligaments stabilising the SI joint. When the biceps femoris contracts, it creates tension in this ligament that directly compresses the SI joint. This makes hamstring strengthening, particularly the long head of the biceps femoris, a specific SI joint stabilisation exercise rather than just a general posterior chain exercise.
Transverse abdominis: The deepest abdominal muscle wraps around the abdomen and its contraction increases intra-abdominal pressure and creates a compressive force across the SI joint via the thoracolumbar fascia. As covered in the isometric core exercises article on this site, the transverse abdominis is specifically targeted through bracing and anti-extension exercises rather than through movement-based core work.
Multifidus: The deep segmental back muscles that attach between the vertebrae and the sacrum. The multifidus provides posterior stabilisation of the SI joint through its sacral attachment and is commonly weakened or inhibited in people with SI joint dysfunction and lower back pain.
Gluteus medius: Prevents the lateral pelvic drop that creates shear forces across the SI joint during single-leg activities. As covered extensively in the hip stabilization exercises article on this site, gluteus medius weakness is one of the most common contributors to asymmetric pelvic loading that stresses the SI joint.
Piriformis: As covered in the stretch piriformis article on this site, the piriformis crosses the SI joint and contributes to its stability through lateral compressive forces. Both weakness and tightness of the piriformis can affect SI joint function.
The Distinction Between SI Joint Pain Types
Not all SI joint pain responds equally to the same exercises. Two primary pain types require different emphasis:
Inflammation-driven SI joint pain:
Characterised by significant joint inflammation (often from conditions such as ankylosing spondylitis, seronegative spondyloarthropathy, or post-partum ligament laxity). Exercise is still beneficial but must be appropriately gentle during acute inflammatory phases.
Instability-driven SI joint pain:
Characterised by insufficient muscular force closure allowing excessive joint movement. Strengthening the force closure muscles (gluteus maximus, transverse abdominis, multifidus, biceps femoris) is the primary treatment. This is the most common presentation in non-inflammatory SI joint dysfunction.
How to identify which type you have:
- Pain that is worse in the morning and improves with movement suggests inflammatory involvement
- Pain that worsens with specific loading positions (single-leg stance, getting out of a car, rolling over in bed) and improves with a sacroiliac belt suggests instability
- Both types benefit from strengthening but at different intensities and progressions
The exercises in this guide are primarily appropriate for the instability-driven type. People with significant inflammatory SI joint conditions should consult a rheumatologist or physiotherapist before beginning a strengthening programme.
Exercises to Avoid During SI Joint Pain
Before covering the strengthening programme, it is worth noting exercises that can worsen SI joint symptoms during active pain phases:
Asymmetric loading of the pelvis: Single-leg exercises performed before adequate stability is established can increase the shear forces on the SI joint rather than stabilising it. This includes single-leg deadlifts, single-leg squats, and lunges during the acute phase.
High-impact activities: Running, jumping, and plyometric activities create repeated impact forces through the SI joint that can worsen symptoms before adequate stabilisation is established.
Deep hip rotation stretches: Aggressive piriformis and hip rotation stretches (pigeon pose, figure four stretches with extreme range) can temporarily destabilise the SI joint by relaxing the muscles that are providing force closure.
Sit-ups and crunches: These exercises load the SI joint in a shear direction that can worsen symptoms. Core training for SI joint stability uses bracing and anti-movement exercises rather than flexion-based movements.
The SI Joint Strengthening Programme
The exercises below are organised to progress from the most basic stabilisation work to the most functional and loaded movements.
Phase 1: Foundation Stabilisation (Weeks 1 to 3)
The goal of Phase 1 is to develop the basic transverse abdominis and multifidus activation, and the foundational gluteal activation, that together provide the initial force closure needed to begin loading the SI joint more specifically.
Exercise 1: Abdominal Bracing
The foundation of SI joint stabilisation. Transverse abdominis activation creates the intra-abdominal pressure and thoracolumbar fascial tension that compresses the SI joint from the front.
How to do it:
- Lie on the back with knees bent, feet flat on the floor
- Breathe normally
- Gently draw the lower abdomen inward and upward, as if trying to pull the navel toward the spine without holding the breath
- The contraction should be gentle (approximately 30 percent of maximum effort), not a forceful bracing
- Hold for 10 seconds while breathing normally
- Release and repeat
- Complete 3 sets of 10 holds, twice daily
Key distinction: This is a gentle activation, not a powerful bracing. Forceful bracing increases intra-abdominal pressure to a level that can actually increase SI joint stress rather than reduce it.
Exercise 2: Pelvic Tilt With Bracing
Combines the abdominal bracing with gentle lumbar movement to develop the transverse abdominis and multifidus co-activation that is specifically impaired in SI joint dysfunction.
How to do it:
- Lie on the back with knees bent, feet flat
- Perform the gentle abdominal brace
- While maintaining the brace, gently tilt the pelvis posteriorly (flatten the lower back toward the floor)
- Hold for 5 seconds
- Release to neutral
- Perform 3 sets of 10, twice daily
Exercise 3: Glute Bridge
As covered in the glute bridges with resistance bands and related articles on this site, the glute bridge is one of the most important SI joint stabilisation exercises because it develops the gluteus maximus, which is the primary active stabiliser of the SI joint through the thoracolumbar fascia.
How to do it:
- Lie on the back with knees bent, feet flat, hip-width apart
- Perform the gentle abdominal brace first
- Drive through both heels to lift the hips to the straight knee-to-shoulder position
- Squeeze the glutes firmly at the top for 2 seconds
- Lower slowly
- Complete 3 sets of 15
The SI joint-specific cue: The abdominal brace before and during the bridge is more important for SI joint stability than for general glute strengthening. The co-activation of the transverse abdominis and the gluteus maximus during the bridge is specifically the force closure mechanism that reduces SI joint shear.
Exercise 4: Clamshell
Develops the gluteus medius to prevent the asymmetric pelvic loading that stresses the SI joint during single-leg activities.
How to do it:
- Lie on the side with a loop band above the knees, hips at 45 degrees, knees at 90 degrees
- Perform a gentle abdominal brace
- Rotate the top knee upward against the band
- Hold for 2 seconds
- Lower slowly
- Complete 3 sets of 15 per side
Exercise 5: Bird Dog
Develops the multifidus and the anti-rotation core stability that maintains SI joint compression during asymmetric limb movements.
How to do it:
- Start on hands and knees in a tabletop position
- Perform a gentle abdominal brace
- Simultaneously extend the right arm forward and the left leg backward
- Hold for 5 seconds with a neutral spine
- Return and repeat on the other side
- Complete 3 sets of 8 per side
The SI joint-specific cue: The diagonal limb loading of the bird dog creates a rotational challenge to the SI joint that the multifidus must resist. The gentle brace ensures the transverse abdominis is providing anterior compressive stabilisation simultaneously.
Phase 2: Progressive Loading (Weeks 4 to 7)
Once the foundational exercises are well-established and symptoms are manageable, progress to more loaded and more functional exercises.
Exercise 6: Single-Leg Glute Bridge
As covered in the single leg glute bridge exercise article on this site, the single-leg version develops the unilateral gluteal strength and pelvic stability that are most relevant to the SI joint demands of walking, stair climbing, and running.
How to do it:
- Set up in the standard glute bridge position
- Perform the abdominal brace
- Extend one leg straight while bridging on the other
- Hold at the top for 2 seconds with the pelvis level
- Lower slowly
- Complete 3 sets of 10 per side
The SI joint-specific emphasis: The pelvis must remain completely level at the top of the single-leg bridge. Any pelvic drop on the extended leg side indicates insufficient force closure from the gluteus medius on the standing side, producing asymmetric SI joint loading.
Exercise 7: Step-Up
Develops the single-leg stance strength in the functional movement most relevant to the SI joint demands of stair climbing and walking.
How to do it:
- Stand facing a step of 20 to 30 centimetres
- Perform a gentle abdominal brace
- Step up with one foot, driving through the working leg to lift the body
- Keep the pelvis level throughout the step-up
- Step back down under control
- Complete 3 sets of 10 per side
Exercise 8: Side-Lying Hip Abduction With Band
More demanding than the clamshell for gluteus medius development, developing the pelvic stability needed for single-leg loading.
How to do it:
- Lie on the side with a band above the knees, body straight
- Lift the top leg against the band to 30 to 40 degrees
- Hold for 2 seconds
- Lower slowly
- Complete 3 sets of 15 per side
Exercise 9: Dead Bug
As covered in the isometric core exercises article on this site, the dead bug specifically develops the anti-extension core stability and the coordinated transverse abdominis and hip flexor activation that are directly relevant to SI joint stabilisation.
How to do it:
- Lie on the back with arms toward the ceiling and knees at 90 degrees above the hips
- Perform the gentle abdominal brace
- Simultaneously lower the right arm overhead and the left leg toward the floor
- Keep the lower back flat against the floor throughout
- Return and alternate
- Complete 3 sets of 8 per side
Exercise 10: Romanian Deadlift (Light to Moderate)
Once the Phase 1 exercises are well-established, the Romanian deadlift develops the biceps femoris and gluteus maximus in the hip hinge pattern most relevant to SI joint force closure during bending and lifting activities.
How to do it:
- As described in the romanian deadlift dumbbell form article on this site
- Begin with a very light load and prioritise the abdominal brace before each rep
- The brace provides the transverse abdominis contribution to SI joint stability during the hip hinge
- Complete 3 sets of 10 at a light load initially
Phase 3: Functional Integration (Weeks 8 to 12)
Progress to bilateral squats, lateral band walks, and the other hip exercises described throughout the hip cluster on this site, as symptoms allow. The exercises in Phase 1 and 2 should continue as maintenance work alongside the more demanding Phase 3 activities.
Exercise 11: Lateral Band Walk
As covered in the lateral band walk exercise article on this site, this develops the gluteus medius endurance that maintains SI joint stability during repetitive single-leg activities like running.
Exercise 12: Goblet Squat
A bilateral squat that develops the overall lower body strength needed for functional activities while the abdominal brace provides SI joint stabilisation throughout.
How to do it:
- Hold a dumbbell or kettlebell at the chest
- Perform the abdominal brace
- Squat to parallel or below while maintaining the brace
- Drive through both heels to return
- Complete 3 sets of 10
Sacroiliac Belt Use
Some people find a sacroiliac belt helpful during the initial phases of rehabilitation, particularly for activities that consistently worsen symptoms (prolonged walking, standing on one leg, climbing stairs). The belt provides additional passive compression of the SI joint, partially supplementing the force closure function of the muscles while they are being strengthened.
The belt should be viewed as a temporary support rather than a long-term solution: its role is to allow participation in strengthening exercises that would otherwise be too painful to perform, while the muscles develop the active stabilisation that will eventually replace the belt’s passive support. Dependence on the belt without concurrent strengthening does not address the underlying instability.
Lifestyle Modifications for SI Joint Management
Avoid prolonged asymmetric postures: Standing with all the weight on one leg, sitting with the legs crossed, and carrying loads on one side all create asymmetric loading of the SI joint. Distributing body weight evenly and varying posture regularly reduce the cumulative joint stress.
Sleep position: Sleeping with a pillow between the knees when lying on the side reduces the rotational force on the SI joint during sleep, which is particularly important when symptoms are acute.
Car entry and exit: Getting into and out of a car is one of the most commonly cited aggravating activities for SI joint pain. Sitting on the seat and swinging both legs in together (rather than stepping in one leg at a time) reduces the asymmetric loading during this transition.
When to Seek Medical Assessment
Seek assessment from a doctor or physiotherapist if:
- SI joint pain is severe and significantly limiting daily function
- Pain is accompanied by any neurological symptoms in the leg (tingling, numbness, weakness)
- Pain has not responded to 4 to 6 weeks of consistent conservative management
- Pain worsens despite appropriate exercise
- You have a known inflammatory condition (ankylosing spondylitis, psoriatic arthritis) that may be contributing to SI joint symptoms
- Symptoms appeared or significantly worsened following a fall or trauma
Frequently Asked Questions
How is SI joint pain different from lower back pain?
SI joint pain typically presents as one-sided pain in the lower back and buttock region, often just below and medial to the posterior superior iliac spine (the dimple in the lower back). It commonly refers into the posterior thigh but rarely extends below the knee. It is specifically aggravated by activities that load the pelvis asymmetrically: single-leg standing, stepping up, getting out of a car. Standard lower back pain from disc or facet joint pathology has different aggravating factors and distribution. A clinical assessment using specific provocation tests (Posterior Shear Test, FABER, Distraction Test) is needed to differentiate SI joint pain from other lower back pain causes.
Can I run with SI joint pain?
Running creates significant repetitive loading of the SI joint through impact and the single-leg stance phase. During acute SI joint pain, running typically worsens symptoms and should be reduced or temporarily stopped. As symptoms improve with the strengthening programme, a gradual return to running can begin, starting with walking and progressively introducing jogging. Running form (avoiding excessive pelvic drop, maintaining good gluteal activation) significantly affects the SI joint loading during running.
Is the SI joint actually a joint or a ligament problem?
Both. The sacroiliac joint is a true synovial joint (with cartilage, joint fluid, and a capsule), but it depends primarily on its surrounding ligaments and muscles for stability rather than on bony architecture. Pain can arise from the joint itself (cartilage, synovial lining), from the surrounding ligaments under excessive stress, or from the muscles that are providing insufficient stabilisation. The strengthening approach in this guide primarily addresses the muscular stabilisation component.
Do I need imaging to know if I have SI joint problems?
Not necessarily. SI joint dysfunction is primarily diagnosed clinically through a combination of symptom history, symptom location, and provocation testing. Imaging (X-ray, MRI) can identify structural changes (erosion, fusion, sclerosis) associated with inflammatory conditions or significant joint degeneration, but normal imaging does not rule out SI joint dysfunction as a pain source. The clinical diagnosis is more reliable than imaging for functional SI joint pain.
How long does SI joint rehabilitation take?
For instability-driven SI joint pain without inflammatory disease, consistent twice-daily Phase 1 exercises typically produce noticeable symptom improvement within 3 to 4 weeks. Meaningful reduction in pain during daily activities typically occurs within 6 to 8 weeks. Full rehabilitation, including the functional integration of Phase 3 exercises and return to unrestricted activity, typically takes 3 to 6 months. Inflammatory SI joint conditions may have a longer and more variable course that is guided by rheumatological management alongside physiotherapy.