The sacroiliac joints link your pelvis and lower spine. They’re made up of the sacrum — the bony structure above your tailbone and below your lower vertebrae — and the top part (ilium) of your pelvis. There are sacroiliac joints in both the right and left sides of your lower back. Strong ligaments hold these joints in place. The sacroiliac joints support the weight of your upper body when you stand.
Sacroiliitis is an inflammation of one or both sacroiliac joints, which can lead to inflammatory low back pain, although some patients remain asymptomatic.
The pain associated with sacroiliitis most commonly occurs in the buttocks and lower back. It can also affect the legs, groin and even the feet. Sacroiliitis pain can be aggravated by:
- Prolonged standing
- Bearing more weight on one leg than the other
- Stair climbing
- Taking large strides
Causes for sacroiliac joint dysfunction include:
- Traumatic injury. A sudden impact, such as a motor vehicle accident or a fall, can damage your sacroiliac joints.
- Arthritis. Wear-and-tear arthritis (osteoarthritis) can occur in sacroiliac joints, as can ankylosing spondylitis — a type of inflammatory arthritis that affects the spine.
- Pregnancy. The sacroiliac joints must loosen and stretch to accommodate childbirth. The added weight and altered gait during pregnancy can cause additional stress on these joints and can lead to abnormal wear.
- Infection. In rare cases, the sacroiliac joint can become infected.
As with other conditions that cause chronic pain, sacroiliitis can result in depression and insomnia.
Sacroiliitis can be linked to spondyloarthropathies (a group of diseases affecting the joints and spine) and it can be defined as a sacroiliac joint dysfunction, which seems to be in a state of altered mechanics. Sacroiliitis is a hallmark of ankylosing spondylitis and may also be seen in the course of other rheumatic and non-rheumatic disorders, such as psoriatic arthropathy, familial Mediterranean fever, Bechet’s disease, hyperparathyroidism and others. Pain caused by sacroiliitiscan be related to either too much or not enough motion in the SI joint. That makes it less a pathological diagnosis and more a patho-mechanical diagnosis.
During the physical exam, the doctor might try to pinpoint the cause of your pain by pressing on places on your hips and buttocks. He or she might move your legs into different positions to gently stress your sacroiliac joints.
An X-ray of your pelvis can reveal signs of damage to the sacroiliac joint. If ankylosing spondylitis is suspected, your doctor might recommend an MRI — a test that uses radio waves and a strong magnetic field to produce very detailed cross-sectional images of both bone and soft tissues.
Because low back pain can have many causes, your doctor might suggest using numbing injections (anesthetics) to help with the diagnosis. For example, if such an injection into your sacroiliac joint stops your pain, it’s likely that the problem is in your sacroiliac joint. However, the numbing medicine can leak into nearby structures, and that can reduce the reliability of this test.
The treatment is depended on the cause. Initial treatment is usually with medications and physical therapy
- Pain relievers. If over-the-counter pain medications don’t provide enough relief, your doctor may prescribe stronger versions of these drugs.
- Muscle relaxants. Medications such as cyclobenzaprine (Amrix, Fexmid) might help reduce the muscle spasms often associated with sacroiliitis.
- TNF inhibitors. Tumor necrosis factor (TNF) inhibitors — such as etanercept (Enbrel), adalimumab (Humira) and infliximab (Remicade) — often help relieve sacroiliitis that’s associated with ankylosing spondylitis.
The physical therapist can help you learn range-of-motion and stretching exercises to maintain joint flexibility, and strengthening exercises to make your muscles more stable. Ultrasound therapy might be adviced for a few days. It helps to reduce the inflammation faster.
Surgical and other procedures
If other methods haven’t relieved your pain, you doctor might suggest:
- Joint injections. Corticosteroids can be injected into the joint to reduce inflammation and pain. You can get only a few joint injections a year because the steroids can weaken your joint’s bones and tendons.
- Radiofrequency denervation. Radiofrequency energy can damage or destroy the nerve tissue causing your pain.
- Electrical stimulation. Implanting an electrical stimulator into the sacrum might help reduce pain caused by sacroiliitis.
- Joint fusion. Although surgery is rarely used to treat sacroiliitis, fusing the two bones together with metal hardware can sometimes relieve sacroiliitis pain.