Definition
Pain arising from the sacroiliac joint, felt in the buttock below L5 and often mistaken for lumbar spine pain.
Aetiology
- Degeneration and post traumatic arthritis
- Pregnancy and ligamentous laxity
- Adjacent segment loading after lumbar fusion
- Spondyloarthropathy including ankylosing spondylitis, infection and crystal arthropathy
Clinical Features
- Unilateral buttock pain below L5, with referral to the groin and thigh
- Pain on prolonged sitting, stairs and rolling over in bed
- Fortin finger sign. Patient points to the posterior superior iliac spine with one finger
- No neurological deficit
Investigations
- Provocation tests include thigh thrust, distraction, compression, sacral thrust and Gaenslen. Three or more positive of six tests had sensitivity 94% and specificity 78% against diagnostic block
- Image guided intra-articular local anaesthetic block. 75% relief is the usual threshold
- Radiographs and MRI to exclude sacroiliitis, infection and fracture
Management
- Physiotherapy. Pelvic stabilisation exercises and a pelvic belt
- Intra-articular corticosteroid. Short term relief
- Radiofrequency ablation. Lateral branch denervation after a positive block
- Sacroiliac joint fusion. Implant fusion for refractory pain after failed nonoperative care
References
Laslett M, Aprill CN, McDonald B, Young SB. Diagnosis of sacroiliac joint pain: validity of individual provocation tests and composites of tests. Man Ther. 2005, 10(3), 207-18. PubMed
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 20 October 2026.