Don’t Confuse Sacroiliac Joint With Hip Joint — How to Sort Out Groin and Buttock Pain Before Deciding Where to Inject Stem Cell Conditioned Media, in the Clinical Order Dr. Moriwaki Follows2026.07.15

“A sharp twinge in the groin when I stand up.” “Sitting in a chair for a long time makes one side of my buttock heavy and dull.” — When patients arrive with complaints like these, answering in a single word whether it is “the sacroiliac joint or the hip joint” is actually not easy. Both are joints adjacent within the same pelvic structure, yet the way the pain presents, aggravating factors, manual findings, and what to look for on imaging are all different. If you skip organizing this and jump straight to a stem cell conditioned media joint injection, you can misjudge where to inject. In this article, we organize the clinical order for sorting groin and buttock pain into sacroiliac-origin or hip-origin, and how to position the injection, from Dr. Moriwaki’s perspective.

Key Points of This Article

・Deep groin pain often originates in the hip; a one-finger point of pain just below the PSIS often originates in the sacroiliac joint. The rule is not to decide on a single symptom alone.

・A stem cell conditioned media joint injection targets different layers — intra-articular, peri-articular, and enthesis — so the layer of inflammation and repair it can address changes with where it is placed. Narrowing down the source of pain before injecting is essential.

・Combine multiple manual findings such as the Patrick (FABER) test, limitation of internal rotation, the Gaenslen test, and the one-finger test with imaging findings to estimate the culprit of the pain.

・Injection is not “magic that rebuilds cartilage.” It is positioned as working on the intra-articular inflammatory environment and the reparative environment of tendon and ligament entheses, with individual variation in indications and limits.

・When the clinical impression is wrong, efficacy assessment also breaks down. So not rushing the injection and firming up the diagnosis first is, in the end, the shortcut.

Why “Sorting” Comes First — The Meaning of a Stem Cell Conditioned Media Joint Injection Changes With Where You Inject

The sacroiliac joint and the hip joint are anatomically close, and patients themselves have difficulty putting into words “which one hurts.” Some describe the deep-buttock heaviness as “low back pain,” while others misinterpret groin tightness as “tight adductors.” Yet a joint injection is treatment that targets different layers — intra-articular, peri-articular, and enthesis — and “where you inject” fundamentally changes which layer of inflammation and repair it addresses. Placing an injection into the hip joint capsule for sacroiliac-origin pain, or around the sacroiliac joint for labral-origin hip pain, is unlikely to produce the expected response.

Representative signs of hip-joint pain

Hip-origin pain tends to appear as deep groin pain or as anterior pain that is confusable with an inguinal hernia. Difficulty sitting cross-legged, inability to cross the leg when putting on socks, and a sharp groin pain when the hip is flexed and internally rotated — findings like these suggest hip-origin pain. By checking joint-space narrowing on X-ray, the CE angle, and labral tears or bone-marrow edema on MRI, conditions such as hip osteoarthritis, FAI (femoroacetabular impingement), and labral tears can be estimated.

Representative signs of sacroiliac-joint pain

On the other hand, sacroiliac-joint pain is known to be suggested by the one-finger test, in which the patient can point with a single finger just below the PSIS (posterior superior iliac spine) and say “it hurts right here.” A pattern of worsening with prolonged sitting and a sharp twinge on the initial movement of turning over in bed or standing up is also typical. Combining multiple pain-provocation tests such as the Patrick (FABER), Gaenslen, and Thigh thrust — and strongly suspecting sacroiliac origin if three or more are positive — is an accumulation of examination steps that matters. The sacroiliac joint is also a joint in which imaging abnormalities are hard to detect, so a pitfall of examination is not to deny the diagnosis on the basis of “no abnormality on MRI” alone.

The Clinical Order Before Considering a Joint Injection

Before deciding “where to inject,” Dr. Moriwaki assembles the examination in the following order. First, sort out the site of pain, aggravating factors, time of day, and history through interview. Next, check manual findings (FABER, limitation of internal rotation, Gaenslen, one-finger test, and so on). Then evaluate structural problems with X-ray and, if needed, MRI. Up to this point, form an impression of whether it is sacroiliac- or hip-origin, and if needed, use a diagnostic block with local anesthetic to check whether the pain is temporarily reduced. Skipping this sequence and jumping to the joint injection makes it impossible even to judge “whether it worked or not.”

Coexistence of both is not rare

What is difficult in clinical practice is that cases in which sacroiliac and hip-origin pain coexist are not few. A patient with hip osteoarthritis, as a result of postural compensation, ends up loading the sacroiliac joint as well — a picture like this is common. In that case, the realistic design is to treat starting from the higher-priority side, and the injection basic operating principle is not to spray broadly into both sides at once or both joints at once, but to focus the aim and watch the response. Past treatment history and current medications also influence the injection plan significantly.

The Range and Limits of Stem Cell Conditioned Media

Stem cell conditioned media is a preparation derived from cellular secretions containing a variety of growth factors and cytokines such as TGF-β, IGF-1, FGF, and VEGF, along with exosomes. It is expected to have the potential to act in the direction of calming the intra-articular inflammatory cycle, and to arrange a reparative environment at tendon and ligament entheses. It is considered in osteoarthritis, enthesopathy, and postoperative chronic pain. However, it is not “an injection that rebuilds cartilage.” In end-stage joint destruction, active infection, or uncontrolled systemic disease, careful judgment of indication is required. Response varies by individual. Efficacy assessment across weeks to months, using pain scores, range of motion, and daily activities as objective indicators, and combining it with rehabilitation and exercise therapy are premises. For general information on joint disease, please refer to the site of the Japanese Orthopaedic Association. If you are considering treatment in the sacroiliac or hip area, please first see details on stem cell conditioned media joint injection here and consult us at a visit.

Frequently Asked Questions

Q. Both my groin and buttock hurt. Can you inject stem cell conditioned media into both?

Cases in which both coexist do occur, but injecting both joints at once from the first session is basically not recommended. Narrowing down the main culprit of the pain and injecting one site first to watch the response is more useful for the subsequent treatment design.

Q. What is a diagnostic block?

It is a test in which a local anesthetic is injected into the suspected joint to see whether the pain is temporarily reduced. It helps distinguish sacroiliac origin from hip origin, but it is not an absolute test — it is interpreted comprehensively together with manual findings and imaging.

Q. How many joint injections does it take to work?

Response varies by individual. It is common to set an induction phase of about 1 to 3 sessions and to assess efficacy with pain scores, range of motion, and daily activities. If response is poor, the option of revisiting the initial clinical impression itself is also considered.

Q. I was told there was “no abnormality on MRI,” but the pain continues. Could the sacroiliac joint be the cause?

Yes. Sacroiliac-joint pain is a representative condition in which imaging abnormalities are hard to detect. Taking manual findings carefully and building up findings from multiple pain-provocation tests is the backbone of the diagnosis.

Q. Does stem cell conditioned media work in end-stage hip osteoarthritis?

When end-stage joint destruction has progressed, the response obtainable from the injection tends to be limited, and consideration of surgical options such as total hip replacement may take priority. For details, please also refer to the joint-injection treatment page.

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Supervising Physician: Shin Moriwaki, MD

Member of the Japan Society of Aesthetic Surgery (JSAS) / Member of the American Academy of Aesthetic Medicine

ECFMG Certificate (US Medical License Qualification)

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AVAN TOKYO Ginza Regenerative Medicine

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