Studies of patients aged at least 18 years with non-specific, non pregnancy-related low back pain, with or without radiation to the lower extremities or groin were eligible for inclusion. Studies needed to compare a diagnostic infiltration of the sacroiliac joint with another diagnostic test or compare any diagnostic test with one of the diagnostic criteria for sacroiliac joint pain according to IASP.
Included studies evaluated the first IASP criterion (pain mapping, pain area or pain referrals from the sacroiliac joint), second IASP criterion (pain provocation or stressing tests), role of different contributors to low back pain, clinical history and mobilisation tests, mechanical examination of the lumbar spin, pain provocation arthrography and bone scintigraphy. All studies included patients with low back pain; in some studies this was required to be chronic. Some studies were restricted to patients with pain below the level of L5-S1 or with pain in the buttock; most studies included patients with pain radiating to the groin or lower extremity.
The reference standard was contrast-enhanced intra-articular injections with local anaesthetic in all studies. Exact details of methods used varied across studies. Most studies were carried out in university hospitals and/or spine centers. Recruitment period, where reported, ranged from seven months to seven years. Patient age ranged from 18 to 87 years. The proportion of women ranged from 38% to 78%.
Two reviewers independently selected studies for inclusion. Discrepancies were resolved through discussion or referral to a third reviewer where necessary.