Lumbosacral pain originating in the sacroiliac joint goes unnoticed far too often, even though it is estimated to accounts for 15% of chronic lower back pain.
It is caused by dysfunction or inflammation of one or both of the sacroiliac joints, which are found below the lumbar spine and just above the coccyx, situated between the sacrum and the pelvis, and are connected by powerful ligaments.
Dysfunction of this joint causes a dull or oppressive pain, usually unilateral, which is alleviated when sitting on the non-painful side, and which worsens when standing or climbing stairs. The pain is located at the base of the lumbar spine, in the buttocks, and may extend to the legs like sciatica, although it does not usually extend below the knee. There are many causes of sacroiliac joint dysfunction, including injury, arthritis, pregnancy and infection.
Ultrasound-guided sacroiliac joint blocks are straightforward and they are performed with the patient lying down, by guiding the needle into the joint using the ultrasound probe, and injecting the drug there.
The effectiveness of sacroiliac joint blocks, with an anaesthetic and corticosteroids, is backed up by solid evidence, and it is recommended when conservative treatment (medication, physiotherapy) fails.