What is the sacroiliac joint?
The sacroiliac joint is a diarthrodial synovial joint that joins the sacrum and ilium. "It is surrounded by a fibrous capsule containing a joint space filled with synovial fluid between the articular surfaces. The sacral capsular surface is composed of hyaline cartilage while the iliac capsular surface is composed of fibrocartilage. Hyaline cartilage is made from type II collagen and is the weakest type of cartilage. Fibrocartilage is made from type I collagen and is the strongest type of cartilage." 
Approximately one third of the sacroiliac joint consists of a synovial joint covered with smooth hyaline cartilage on both surfaces – features typical of other joints capable of movement (shoulder, knee, hip, etc). The remaining two thirds of the sacroiliac joint consist of a cartilaginous joint that is composed primarily of the posterior sacroiliac ligament with flexible, yet tough fibrocartilage (think annulus fibrosis of the intervertebral disc, menisci, pubic symphysis) on the bone surfaces.
How big is the sacroiliac joint?
The sacroiliac joint is the largest joint in the axial skeleton of the human body.  While there is considerable variability in the amount of total surface area between individuals (5-20cm2), the average has been observed to be approximately 12cm2 for adult females and 13cm2 for adult males.  By comparison, the average surface area of the acetabulum (hip joint) is 28.8 cm2 .
How stable is the sacroiliac joint?
The sacroiliac joint is one of the most stable joints in the body. The joint surfaces of the sacroiliac joint are ear-shaped and have portions of the same surfaces positioned in different planes appearing to limit motion rather than facilitate it. The sacroiliac joint is then stabilized by a complex cluster of some of the strongest ligaments in the body that limit movement in every plane of motion. These features have led some to conclude that the sacroiliac joint is designed more for stability than mobility: “The SIJ should be classified anatomically as a symphysis [an immovable joint where two bones are closely joined] with some characteristics of a synovial joint.” 
Does the sacroiliac joint move?
Yes, the sacroiliac joint does move - just not in every person. The sacroiliac joint moves a little in healthy young persons. But, in most persons aged 55 and older, the sacroiliac joint is naturally fused and doesn't move at all due to extensive ridging of the joint surfaces as well as ossification of the interosseous sacroiliac ligament.
Sturesson et al  studied 25 patients with suspected SIJ disorders using roentgen stereophotogrammetry [RSA] in physiologic positions as well as in the extreme of physiologic positions. RSA is a highly accurate assessment of three-dimensional migration and micromotion of a joint by placing small markers percutaneously into relevant structures within the body and then taking a stereo image with two synchronized x-ray foci. In this study, markers were implanted into the sacrum and the ilium, and x-rays were taken in end-range positions. Movement was indeed observed in the sacroiliac joints.
However, Rosatelli et al  studied the anatomy of the interosseous region of the sacroiliac joint in cadavers and stumbled across a remarkable finding: “Surface characteristics of the SIJ complex observed in specimens 55 years of age or older included moderate to extensive ridging of the interosseous region of the sacrum and ilium in 100% of specimens and ossification of the central interosseous region of the sacroiliac ligament in 60% of specimens.”
Their conclusion? “Central region ossification of the interosseous SI ligament and the presence of ridges and depressions over the opposing interosseous surfaces of the sacrum and ilium are features common to specimens that are in or beyond their sixth decade. These findings further support the contention that there is little to no movement available at this joint in older individuals.”
How much does the sacroiliac joint move?
The sacroiliac joint does not move at all in most persons aged 55 and older as it is naturally fused by extensive ridging of the joint surfaces as well as ossification of the interosseous sacroiliac ligament. And, even in healthy young persons, there is only minute movement. A study by Sturesson et al found that the degrees of rotation were small with a mean of 2.5 degrees (0.8-3.9) and translation was minute with a mean of 0.7 mm (0.1-1.6 mm). This study was later validated in a systematic review by Goode et al : “Rotation ranged between –1.1 to 2.2 degrees along the X–axis, –0.8 to 4.0 degrees along the Y-axis, and –0.5 to 8.0 degrees along the Z-axis. Translation ranged between –0.3 to 8.0 mm along the X-axis, –0.2 to 7.0 mm along the Y-axis, –0.3 to 6.0 mm along the Z-axis.”
Can the sacroiliac joint hurt?
Yes, it is possible to experience pain in the sacroiliac joints. A study by Sembrano et al observed: "The SI joint is... richly innervated by a combination of unmyelinated free nerve endings and the posterior primary rami of L2-S3." [1-10]
Later, Wong et al wrote: "The sacroiliac joint is well innervated but the pattern of innervation varies among individuals. The sacroiliac joint receives its innervation from the ventral rami of L4 and L5, superior gluteal nerve, and dorsal rami of L5-S2. The nerve supply to the SI joint varies between individuals and innervation may be almost exclusively derived from the sacral dorsal rami." 
Where does the sacroiliac joint refer pain?
The sacroiliac joint may refer pain up to 10 cm below the sacroiliac joint and up to 3 cm laterally to it. A study by Fortin et al  used provocative injections into the right sacroiliac joint of 10 asymptomatic volunteers to determine where they would experience pain. "The injections consisted of contrast material followed by Xylocaine. All 10 individuals experienced discomfort upon initial injection, with the most significant sensation felt directly around the injection site. Subsequent sensory examination revealed an area of hypesthesia [decreased sensation] extending approximately 10 cm caudally and 3 cm laterally from the posterior superior iliac spine. This area of hypesthesia corresponded to the area of maximal pain noted upon injection."
Other studies have proposed that the sacroiliac joint can produce different and unique referral patterns including groin pain, posterolateral thigh pain, and lateral lower leg pain that may mimic a radiculopathy. [11-13, 24] However, these studies had some serious methodological flaws that, I would argue, made their diagnosis of sacroiliac joint pain invalid. More on that to come.
Can the sacroiliac joints dislocate, subluxate, or go out of alignment?
Yes, the sacroiliac joints can dislocate, subluxate, or go out of alignment. However, this is exceedingly rare and has only been documented in cases of severe trauma. A study by Yoon et al included 73 patients with a straddle fracture injury (fracture of both superior and inferior pubic rami). Of the 73 patients, 56 (77%) had a posterior pelvic ring injury and 7 died. In 43 patients, the posterior pelvic ring injuries constituted unstable pelvic injury and were treated surgically. Sacroiliac joint dislocation [occurred] in 18." 
But, the sacroiliac joint doesn't have to be dislocated to cause pain. When comparing the motion of a painful sacroiliac joint with the motion of the pain-free side in 25 subjects, Sturesson et al noted that "there was no difference [in motion] between symptomatic and asymptomatic joints." 
Can the sacroiliac joints be realigned, adjusted, or popped back into place?
No, the sacroiliac joint cannot be realigned, adjusted, or otherwise popped back into place conservatively. In the exceedingly rare event that a sacroiliac joint did get dislocated during severe trauma, surgical fixation is the only plausible treatment option.
After a manual therapy technique - a high-velocity low-amplitude (HVLA) thrust manipulation - targeting the sacroiliac joints was performed on a group of study subjects (not involved in severe trauma), Tullberg et al observed that it was "not accompanied by altered position of the sacroiliac joint".  So, the question is: If a HVLA thrust manipulation did not change the position of the sacroiliac joint, how plausible would it be that other manual techniques or exercises involving less speed and force would be able to do so?
Interestingly, however, the authors remain firm and "are convinced that something happens when manipulating the SIJ" and they've observed "a good clinical outcome after SIJ manipulation." They're onto something there! More on this later.
How common is sacroiliac joint pain?
The prevalence of sacroiliac joint pain is estimated to be between 13-30% in individuals with chronic low back pain [11-13] (and estimated to be as high as 43% in patients after lumbar fusion surgery ). But, I propose the prevalence of sacroiliac joint pain is considerably lower, and my reasons will be presented as we dig into the details of these studies on sacroiliac joint prevalence.
One study by Sembrano et al  comments, “Our finding that the SI joint is a significant pain generator in 14.5% of low back pain patients is very similar to the 18.5% and 13 to 30% findings in the studies of Maigne et al  and Schwarzer et al , respectively. Both studies used diagnostic injections as a reference standard.” So, it does appear that there is a general consensus here, and I've found that most subsequent studies on sacroiliac joint dysfunction have anchored on these figures indiscriminately. But, let's dig deeper.
Regarding the use of diagnostic injections as the reference standard, the injection is best performed using fluoroscopy or CT and contrast. Rosenberg et al  have shown that only 22% of ‘‘blind’’ injections were actually in the joint space. To further confound the issue, there is no guarantee that the injectate is limited exclusively to the sacroiliac joint and does not bleed out - extra-articular spread - and affect other structures such as the lumbar plexus, resulting in false positives.
Sembrano et al then qualifies the estimate of 13-30%:
“Our study has a number of obvious limitations, foremost of which is the lack of a formal diagnostic algorithm implemented during the period of study. Diagnostic workup was performed on the discretion of the treating spine surgeon appropriate to the clinical diagnosis, which, in turn, was based on a synthesis of all available information from the history, physical examination, and imaging studies at the time."
This requires some pause. First of all, no study to date that I'm aware of has concluded that imaging of any kind is helpful in diagnosing sacroiliac joint dysfunction. Second, the subjective interview does not appear to add much value in diagnosing sacroiliac joint pain. Dreyfuss et al concluded: "No historical feature... demonstrated worthwhile diagnostic value."  (More on that in the next section.) And third, the physical examination also falls well short of being incredibly helpful and reliable in diagnosing sacroiliac joint pain as I'll discuss in detail later.
But, the other limitation for diagnosing sacroiliac joint pain is the lack of a gold standard. Returning to the Sembrano et al study: “Ultimately, perhaps the most important limitation of this study pertains to the accuracy of the diagnoses arrived at in each case. Although methods and modalities used were what are presently considered standard armamentarium in the investigation of LBP tempered by physician discretion, none of these could claim 100% accuracy. For example, even as discography has become widely used, its validity to this day remains controversial, in part because postdiscography surgical outcomes have been inconsistent. For epidural injections, sensitivity figures between 65% and 100%, and specificity between 71% and 95% have been quoted. However, obtaining accuracy estimates for spinal injection techniques (e.g.,facet blocks, epidural injections, and selective nerve root blocks) have been problematic primarily because there is no available gold standard that would measure presence or absence of pain to compare them against. Some statements on accuracy may be inferred from reproducibility studies (screening and confirmatory injections) and surgical outcomes. Although the former could measure false positivity and reliability, the limitations of using surgical outcomes as reference standard have already been discussed.”
With the aforementioned limitations, the best we can say at this point is that an estimated 13-30% of patients with chronic low back pain are suspected as having sacroiliac joint dysfunction responsible for their symptoms by these authors. However, it’s not possible to validate that estimate at this time – we simply don’t know how many truly do because there is no gold standard for diagnosis currently available. It is my professional opinion that the actual prevalence of true sacroiliac joint pain is considerably lower than these estimates, and my reasons are provided along with the scientific studies that will be considered a bit later.
What causes sacroiliac joint pain?
There have been many proposed causes of sacroiliac joint pain, but no mechanism of injury has been scientifically correlated with the sacroiliac joint except for cases of severe trauma . Some clinicians specifically inquire about an asymmetrical trauma to the pelvis that could stress the sacroiliac joint – a slip and fall, an unanticipated step down from a curb or into a hole, a motor vehicle accident with one foot on the brake, etc. Others place value on aggravating activities that they suspect would provoke sacroiliac joint pain such as putting on socks, walking up or down stairs, getting into or out of bed, rolling over in bed, bearing weight through the painful side in standing, and the act of standing up from a seated position.
One study set out to determine if any of these potential mechanisms of injury or aggravating activities could be used toward diagnosing sacroiliac joint pain. Dreyfuss et al  gathered a panel of experts from various disciplines including rheumatology, orthopedic surgery, clinical anatomy, orthopedic medicine, chiropractic, manual therapy, physiatry, osteopathy, and radiology to recommend which examination techniques would likely be most helpful in diagnosing sacroiliac joint dysfunction.
Then, historical data was gathered from 85 patients who were then examined and subsequently underwent sacroiliac joint injections with a local anesthetic as the diagnostic reference standard (see the section above for a discussion on the limitations of using intra-articular injections as a diagnostic standard).
Patients were asked if any of the following treatments were used and what effect each treatment had (increased, decreased, or did not affect their pain): anti-inflammatory medications, muscle relaxers, physical therapy, home exercise, application of local heat and cold, and manual manipulations of the sacroiliac joint.
Patients were also asked if a specific, traumatic event caused their pain and if this event was caused by twisting, heavy lifting, a fall on the buttocks, a motor vehicle accident, a fall in a hole, a sports-related injury, a repetitive work injury, or another type of injury.
Patients were then asked if the following activities increased, decreased, or did not affect their pain: walking, sitting, lying down, standing in place, wearing high heels or boots, straining with a bowel movement, coughing or sneezing, and usual job activities. Which of all of these components do you think correlated well with sacroiliac joint dysfunction?
None of them.
The study concluded: “No aggravating or relieving factor was of value for diagnosing the presence of sacroiliac joint pain as established by intra-articular blocks. All of these features in the patients’ medical history had poor sensitivity, poor specificity, or both.”
Unfortunately, it appears that these subjective details are unhelpful in diagnosing sacroiliac joint pain. Additionally, I would argue that none of these aggravating activities would affect only the sacroiliac joint. Wouldn't the lumbar spine or hip joints be involved as well? These aggravating activities are simply not able to differentiate between these neighboring structures.
However, one component of the subjective examination may be worth considering as we'll next discuss.
How is sacroiliac pain diagnosed?
A recent systematic review concluded that "SIJ diagnostics remain difﬁcult and uncertain. There is no typical pain pattern; there are substantial contradictions in the analysis of the innervation. Today, there is still no gold standard in SIJ diagnostics. The clinical examination of function is not reliable and reproducible. Chronic pain in the area of the SIJ may also be a referred pain of any nocigenerator in any structure segmentally innervated from L5 to S3. However, the most reliable way to diagnose sacroiliac joint pain includes "at least three [provocation] tests with the same result, an experienced examiner, gluteal pain, good positive or negative pre-test probability.” Let's unpack all of that.
As covered in the previous section, the subjective interview is largely unhelpful in diagnosing SIJ pain. However, there is some evidence that one particular component of the subjective interview may provide some benefit. In the study we'll consider, each patient was asked to point with one finger to the region of pain which was then marked on a body chart by the observer. If the following criteria were met, a patient was considered to have a positive "Fortin finger test": 1) The patient could localize the pain with one finger. 2) The area pointed to was immediately inferomedial to the posterior superior iliac spine (PSIS) within 1 cm. 3) The patient consistently pointed to the same area over at least two trials. “The Fortin finger test was used as a means to identify patients with low back pain and sacroiliac joint dysfunction. Provocation-positive sacroiliac joint injections were used to ratify or refute the applicability of this new clinical sign for identification of patients with sacroiliac joint dysfunction. Sixteen subjects were chosen from 54 consecutive patients by using the Fortin finger test. All 16 patients subsequently had provocation-positive joint injections validating sacroiliac joint abnormalities.” 
Let's move on to the physical examination. Is there evidence that any particular test or examination technique can assist with the diagnosis of sacroiliac joint pain? Well, it doesn't appear that palpation or motion testing has any utility. Sturesson et al noted: “Twenty-five patients with SIJ disorders were studied with roentgen stereophotogrammetry (RSA) in physiologic positions as well as in the extreme of physiologic positions. There was a constant pattern of motion with different load, especially around the transverse axis. The degrees of rotation were small and in mean between extreme positions 2.5 degrees ranging from 0.8-3.9 degrees. The translation was, mean, 0.7 mm (0.1-1.6 mm). There was no difference between symptomatic and asymptomatic joints." They concluded: “Motion of the SIJ is limited to minute amounts of rotation and of translation suggesting that clinical methods utilizing palpation for diagnosing SIJ pathology may have limited clinical utility.” 
So, if palpation and motion testing don't seem to be helpful, where do we go from here? Well, Laslett et al found that tests that stress the SIJ in order to provoke familiar pain have acceptable inter-examiner reliability and have clinically useful validity against an acceptable reference standard. Three or more positive pain provocation SIJ tests have sensitivity and specificity of 91% and 78% respectively – in the absence of centralization with repeated motions or sustained positions of the lumbar spine.  The tests included in this study were distraction, compression, thigh thrust, Gaenslen's test, sacral thrust, and Patrick's FABER test.
Has the Laslett study been validated? Yes, a review and meta-analysis by Szadek  showed that a positive thigh thrust test, a positive compression test, and a total of three positive provocation tests have discriminative power for diagnosing SI joint pain, using diagnostic injections as the reference standard.
Szadek doesn't leave it at that, however: “It is surprising, however, that the selective inﬁltration targets only the joint cavity. Taking the basic anatomy of the SI joint into account, one may assume that the complaints originating from the SI joint could also involve neighboring SI joint ligaments. On the other hand, injecting even a very small volume of a local anesthetic into the joint cavity does not prevent leakage to the neighboring nerve structures and ligaments. Consequently, there is a possibility that using this technique, more structures are targeted than the intra-synovial space."
Please note their word of caution: “Because a gold standard for sacroiliac joint pain diagnosis is lacking, the diagnostic validity of tests related to the IASP criteria for SI joint pain should be regarded with care.” Please read that again carefully. There is no gold standard for sacroiliac joint pain diagnosis.
But, can't we at least hang our hats on these SIJ provocation tests? Not so fast. A systematic review by Klerx et al that considered the Laslett et al and Szadek studies among others observed: "With respect to pain provocation tests, systematic reviews revealed poor reliability and validity. One review showed better diagnostic accuracy values but still concluded that 'the usefulness of these tests in clinic still remains unclear'. A review on the diagnostic validity of the International Association for the Study of Pain (IASP) criteria to diagnose SIJ pain concluded that the thigh thrust test, the compression test, and three or more positive stress tests had discriminative power to diagnose SIJ pain. Considering the lack of a criterion standard for SIJ pain, the diagnostic validity of tests related to the IASP criteria for SIJ pain should be considered with care." 
VonHeymann et al  summarizes well the continued uncertainty surrounding sacroiliac joint dysfunction: “SIJ diagnostics remain difﬁcult and uncertain. There is no typical pain pattern; there are substantial contradictions in the analysis of the innervation. Today, there is still no gold standard in SIJ diagnostics. Even Rx (ﬂuoroscopically)-guided intra-articular injections do not have reliable results. Many irritation zones/points have been described . The clinical examination of function is not reliable and reproducible. In addition, we have to take into consideration that the perception of pain at a certain point of the anatomy does not mean that the nocigenerator of this pain is exactly where the brain locates that pain. This means that a chronic pain in the area of the SIJ may also be a referred pain of any nocigenerator in any structure segmentally innervated from L5 to S3. Is there reliable information from the clinical ﬁndings at all? In this respect, the publications are conﬂicting and not unanimous. Nevertheless, these studies present some general ideas: Not reliable are: one single test, an inexperienced examiner, and SIJ pain combined with low back pain. Reliable are: at least three pain tests with the same result, an experienced examiner, gluteal pain (also pseudo-radicular leg pain), good positive or negative pre-test probability, pain provocation is more reliable than palpation of mobility.”
Most recently, another systematic review by Saueressig et al calculated that a positive pain provocation test cluster gives only 30% certainty of ruling in sacroiliac joint pain, while a negative pain provocation test cluster gives 92% certainty of ruling out SIJ. They conclude: "Clusters of pain provocation tests for the SIJ do not provide sufficient diagnostic test accuracy for SIJ pain."
So... quite a bit of uncertainly remains around the diagnosing of sacroiliac joint pain.
What's the Best Evidence-Based Conservative Treatment for Sacroiliac Joint Pain?
High-velocity low-amplitude thrust manipulation is the best evidence-based conservative treatment for sacroiliac joint pain. A 2017 systematic review by Al-subahi concluded: "Physiotherapy interventions are effective in reducing pain and disability associated with sacroiliac joint dysfunction, with manipulation being the most effective approach... Manipulation, exercise and kinesio tape are effective in the treatment of pain, disability and pelvic asymmetry in SIJD."  Therefore, start by finding an experienced physical therapist who specializes in orthopedic manual physical therapy.
Do Sacroiliac Belts Work?
SI belts may decrease pain in some individuals. Soisson et al observed: "Nine of 17 patients reported decreased pain intensities under moderate belt application, four reported no change and four reported increased pain intensity."  Here is a link to the specific brand of sacroiliac belt used in the study: the Bauerfeind SacroLoc Back Support. Of course, less expensive options are available that don't have the backing of scientific research.
Does Regenerative Medicine (such as Stem Cells or PRP Injections) Help Sacroiliac Joint Pain?
Sanapati conducted a systematic review with meta-analysis to determine whether or not regenerative medicine therapies provide long-term relief in chronic low back pain, including sacroiliac joint pain. Specifically, they wanted to uncover the effectiveness of medicinal signaling cells or mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) injections in managing low back pain. They included 12 lumbar disc, 5 epidural, 3 lumbar facet joint, and 3 sacroiliac joint studies. Their findings? "The findings of this systematic review and single-arm meta-analysis shows that MSCs and PRP may be effective in managing discogenic low back pain, radicular pain, facet joint pain, and sacroiliac joint pain, with variable levels of evidence in favor of these techniques."  However, this study was limited due to the number of studies included and a lack of high quality randomized controlled trials (RCTs).
Does Sacroiliac Joint Fusion Surgery Help Sacroiliac Joint Pain?
Sacroiliac joint fusion surgery may be an appropriate option for a select group of patients with severe pain that do not improve with the latest evidence-based orthopedic manual physical therapy performed by an experienced and qualified physical therapist. However, it remains unclear which patients would benefit from surgery, and this decision must be weighed along with the possibility of adverse events and complications during and after surgery. Additionally, it begs the question: If the sacroiliac joint barely moves in health young individuals and becomes naturally fused in the majority of persons 55 years and older, does pain located in the area of an incredibly stable - even fused - joint require... surgical stabilization? The obvious answer is... no. (Of course, severe and life-threatening trauma certainly would require surgical stabilization). However, some patients who undergo surgery report decreased SIJ pain - likely by way of other pain-relieving physiological mechanisms.
Kibsgard et al reported: "In paper III, we used a single-subject design study to evaluate the outcomes of pain, disability and health-related quality of life 1 year after SIJ fusion in 8 patients with severe PgP [pelvic girdle pain]. These patients were included by applying strict inclusion and exclusion criteria, and they were submitted to surgery with anterior unilateral SIJ fusion combined with a fusion to the pubic symphysis. One year after open unilateral anterior SIJ fusion combined with symphysis pubis fusion, positive and significant changes in both physical function and pain were observed. Despite these positive results, this procedure was associated with adverse events and complications.
"In the last paper, paper IV, we performed a long-term follow-up of 50 patients who underwent SIJ fusion performed by Sudmann in hagavik, bergen, norway. All of the patients completed a questionnaire that measured the outcomes of pain, disability and health-related quality of life, and these outcomes were compared with the 1-year outcomes collected by the Sudmann. A comparison group of 28 patients who did not receive SIJ fusion completed the same questionnaire. Patients with chronic PgP who underwent SIJ fusion reported being moderately disabled, with moderate or severe pain intensity 23 years after surgery. Approximately half of these patients had successful 1-year outcomes, and in these patients, good results were sustained 23 years after surgery. Two-thirds of the patients experienced a positive long-term effect from fusion surgery, and 20% reported no effects from the surgery. It appeared that this surgery was an appropriate treatment option for a select group of patients with severe PgP, but which patients would benefit from surgery remains unclear." 
Open Surgery vs Minimally Invasive Surgery for Sacroiliac Joint Pain
The rate of complications appears to be lower in minimally invasive surgery for sacroiliac joint pain.
Lingutla performed a systematic review with meta-analysis of 6 observational case series: "In this meta-analysis of the six studies that included usable data, which excluded the foregoing studies, three reported results using MIS [minimally invasive surgery], two used open methods, and one study used both. The analysis has found that patients undergoing SIJF [sacroiliac joint fusion] for PGP [pelvic girdle pain] had a statistically and clinically signiﬁcant improvement in pain relief, ODI [Oswestry Disability Index], SF-36 [36-Item Short Form Survey] and Majeed score. Complications due to the surgery were low and occurred in 16 patients out of 307 (5.2 %). For the open surgery the rate was 5.44 and 3.49 % for the MIS methods."
However, it cautions, "Although this meta-analysis has shown functional and pain outcomes to be statistically and clinically signiﬁcant, the conclusion is based upon very limited data and therefore its validity may be low." 
Physical Therapy vs Surgery for Sacroiliac Joint Pain
Unless, your sacroiliac joint was fractured or dislocated due to severe and life-threatening physical trauma, always start with orthopedic manual physical therapy - the costs and risks are exponentially lower and, if you don't respond to physical therapy, surgery remains an option. There currently is no high-quality scientific research that compares the two interventions. But, let's consider one study that appears to have been deliberately designed to showcase surgery as superior to physical therapy. Here's a summary before we dig deeper into its obvious flaws:
Dengler randomized 103 subjects into two groups - physical therapy or sacroiliac joint arthrodesis. Here's what they observed: "At 2 years, the mean low back pain improved by 45 points after sacroiliac joint arthrodesis and 11 points after conservative management, with a mean difference between groups of 34 points. The mean ODI improved by 26 points after sacroiliac joint arthrodesis and 8 points after conservative management, with a mean difference between groups of 18 points. Parallel improvements were seen in quality of life. In the sacroiliac joint arthrodesis group, the prevalence of opioid use decreased from 56% at baseline to 33% at 2 years, and no significant change was observed in the conservative management group (47.1% at baseline and 45.7% at 2 years). Subjects in the conservative management group, after crossover to the surgical procedure, showed improvements in all measures similar to those originally assigned to sacroiliac joint arthrodesis. In the first 6 months, the frequency of adverse events did not differ between groups. By month 24, we observed 39 severe adverse events after sacroiliac joint arthrodesis, including 2 cases of sacroiliac joint pain, 1 case of a postoperative gluteal hematoma, and 1 case of post-operative nerve impingement. The analysis of computed tomographic (CT) imaging at 12 months after sacroiliac joint arthrodesis showed radiolucencies adjacent to 8 implants (4.0% of all implants)." 
Unfortunately, this was not a valid comparison, and the results of this study are thus meaningless. The only detail provided about the conservative care group is: "Subjects assigned to conservative management underwent a mean of 25 physical therapy sessions over the first 6 months." That is incredibly unhelpful. Who performed the physical therapy? Were they doctors of physical therapy, or were they assistants or unlicensed support staff? If they were doctors of physical therapy, were they board-certified in orthopedics? Were they fellowship-trained in orthopedic manual physical therapy? How many years of experience did they have? What physical therapy interventions were performed? Was orthopedic manual physical therapy included? Were the treatment interventions based on the best available scientific evidence?
This glaring omission of detail regarding the conservative care group is unforgiveable. What if the same study were conducted with the opposite approach: comparing one very specific technique in orthopedic manual physical therapy for sacroiliac joint pain performed by fellowship-trained doctors of physical therapy against... "medical care" with absolutely no details provided about this "medical care"? That would likewise be meaningless. Who provided this medical care? And, what medical care? Medications? If so, what kind? Injections? If so, what kind? Surgery? If so, what kind?