Condition Guide · Brighton & Hove
SI joint pain is one of the most commonly overlooked causes of low back and buttock pain. Accurate identification and targeted treatment produces excellent results.
Understanding SI Joint Pain
The sacroiliac (SI) joints connect the sacrum at the base of the spine to the iliac bones of the pelvis on each side. They are large, strong joints that transmit load between the spine and the lower limbs and have a very limited but important range of movement. SI joint dysfunction occurs when this joint becomes either hypomobile (stiff and restricted) or hypermobile (insufficiently stable), producing pain in the lower back, buttock and sometimes the leg.
SI joint pain accounts for an estimated 15-25% of low back pain presentations, yet it is frequently misdiagnosed as lumbar spine pathology. The two can co-exist, but treating a lumbar problem that is primarily sacroiliac in origin will produce limited and temporary results.
SI joint pain cannot be reliably diagnosed from imaging alone. X-rays and MRI frequently show changes in the SI joint in people with no pain, and may appear normal in symptomatic patients. Accurate diagnosis requires a cluster of clinical provocation tests, of which the posterior shear test, distraction test and compression test are the most reliable. No single test is definitive, but a cluster of positive tests combined with the clinical picture produces a reliable diagnosis.
Pregnancy and the postpartum period are the most common precipitants of SI joint dysfunction, due to the combined effects of relaxin-induced ligament laxity and altered loading mechanics. Leg length discrepancy, scoliosis, previous lumbar fusion surgery and sports involving asymmetric loading (golf, cricket, rowing) also increase SI joint stress. Inflammatory arthritis including ankylosing spondylitis can produce SI joint inflammation and should be considered in younger patients with morning stiffness lasting more than 30 minutes.
Pelvic girdle pain, which frequently involves the SI joints, affects up to 25% of pregnant women. The relaxin-induced ligament laxity that allows pelvic expansion for birth also reduces SI joint stability. Symptoms typically resolve postpartum but can persist, particularly with subsequent pregnancies. Targeted stabilisation exercises and appropriate manual therapy are safe and effective both during and after pregnancy.
Recognising SI Joint Pain
Pain centred over the posterior superior iliac spine, one finger-breadth below and medial to the PSIS. The classic location that patients point to with one finger.
Pain particularly with rising from sitting, turning in bed, climbing stairs and walking up inclines. Activities that involve asymmetric pelvic loading.
Pain can refer into the groin, outer thigh and occasionally below the knee. Distinguished from true sciatica by the pattern and absence of neurological signs in most cases.
Pain when lying on the affected side. Turning in bed is particularly symptomatic. Many patients report this as one of the most disruptive features.
Walking, running and activities involving weight-bearing on one leg provoke symptoms. Sports with rotational components are particularly aggravating.
Prolonged sitting, particularly asymmetric sitting with weight through the affected side, aggravates symptoms. Standing relief is common.
Treatment Approach
Treatment depends on whether the dysfunction is primarily hypomobility or hypermobility, as the approach differs significantly between the two.
A cluster of provocation tests to confirm SI joint involvement and determine whether hypomobility or hypermobility is the primary driver, before any treatment.
For hypomobile SI joint presentations, specific mobilisation techniques to restore normal joint movement and reduce pain from joint restriction.
For hypermobile presentations, particularly post-pregnancy, a structured programme targeting the deep stabilisers of the pelvis including the transversus abdominis and glute medius.
Targeted work to the piriformis, gluteal muscles and thoracolumbar fascia that become secondary pain sources alongside the primary SI joint dysfunction.
Effective for the gluteal and piriformis trigger points that develop as compensation for altered pelvic mechanics in SI joint dysfunction.
A sacroiliac belt can provide meaningful symptom relief for hypermobile presentations, particularly during pregnancy and the early postpartum period. Guidance on correct application and when to use it.
Accurate diagnosis and targeted treatment produces excellent results for SI joint dysfunction. Don't assume your buttock or back pain is a lumbar problem without a proper assessment.