What Is Sacroiliac Joint Pain, and Why Is It Confused With a Herniated Disc?
The SI joint transfers the load of the trunk to the legs; it moves very little but carries great force. Childbirth, trauma, leg-length difference, one-sided strain, prolonged sitting or degenerative changes can turn this joint into a source of pain. The pain is typically just above the buttock, beside the tailbone, and usually one-sided; it increases on standing up from sitting, climbing stairs, or bearing weight on that side. The reason it is confused with a herniated disc is that the pain can spread to the buttock and sometimes to the upper-back part of the leg. But the difference matters: SI joint pain usually does not go below the knee, does not radiate to the toes, and does not cause marked loss of muscle strength. Seeing SI joint degeneration on MRI alone does not establish the diagnosis; examination tests and, where needed, a diagnostic block are essential.
Diagnosis: Why Is the SI Joint Block Decisive?
Diagnosis in SI joint dysfunction is difficult, because no single examination test or imaging gives a definite answer on its own. Therefore, if several provocation tests are positive and the clinical picture fits, a diagnostic SI joint block is performed under fluoroscopy to confirm the diagnosis: a local anaesthetic is delivered into the joint and it is observed whether the patient's pain decreases markedly and temporarily. This block is the most reliable method to show that the pain truly arises from the SI joint, and it prevents unnecessary treatments. If the block does not relieve the pain, the source is most likely another structure (lumbar disc, facet joint, hip joint), and directing treatment to the SI joint would be wrong. Here too, the determinant of success is not the procedure but the correct diagnosis.
Non-Surgical Treatment: Injection and Radiofrequency (RF)
The first step in SI joint dysfunction is always non-surgical: pain-reducing medication, well-targeted physical therapy and exercise, posture and gait adjustment, and where needed an insole for leg-length difference. If these measures are insufficient, a therapeutic injection containing corticosteroid into the joint can reduce inflammation and pain. When a more lasting effect is needed, radiofrequency (RF) can be applied to the nerve branches supplying the joint to suppress pain transmission. The honest expectation is this: these methods do not make a structural 'repair' to the joint; they aim to manage pain. The effect of an injection may be limited to weeks or months and that of RF to months, and the pain may recur as the nerve branches regenerate. In a correctly selected patient these interventional methods can markedly improve quality of life and make surgery unnecessary; but no definite guarantee can be given to any patient.
When Is Non-Surgical Enough, and When Is Surgery Needed?
The great majority of SI joint dysfunction is managed with non-surgical methods; surgery (SI joint fusion) is considered only in a very selected group of patients — correctly diagnosed, with a clear response to the diagnostic block, but whose pain persists and severely limits life despite all conservative and interventional steps. The honest frame is this: SI surgery is not right in every case and may bring no benefit if applied unnecessarily. At the same time, if the source of the pain is not actually the SI joint, no SI treatment (neither injection, nor RF, nor fusion) will work; this is why a solid diagnosis comes before everything. The aim is neither unnecessary surgery nor leaving a real problem in limbo; the decision is made by evaluating the diagnostic block response, imaging and clinical picture together.
Recovery, Expectations and Risks
SI joint injection and RF are closed interventions done on an outpatient basis; most patients return to daily life shortly after the procedure. However, relief is not always immediate and may be gradual. The realistic picture: in a correctly diagnosed patient, meaningful relief may be seen, but the effect may not be permanent and is repeated when needed. No intervention is without risk; in these needle-based procedures, possibilities such as infection, temporary numbness and pain at the site, although rare, exist and are discussed during informed consent. No guarantee of a 'definite and permanent solution' can be given for any method. In the long term, strengthening the core muscles, correct posture, weight control and correcting any leg-length difference are the basic measures to reduce recurrence of SI joint pain.