Private stem cell treatment for knee osteoarthritis in Japan can cost about ¥1.1 million to ¥2.8 million for one knee or one treatment site, based on current MHLW-published treatment documents. One fat-derived MSC plan lists ¥1.1 million, another lists ¥1.815 million, and a synovial stem cell plan lists ¥2.8 million for one knee.[1][2][3]
These are prices from specific treatment plans, not a national average. A lower price can still lead to a higher final bill if tests, tissue collection, cell culture, another injection or follow-up are charged separately. Japanese self-pay treatment prices also vary by cell type and treatment method, as shown in the wider stem cell treatment costs in Japan data.
What You May Pay
| Published example | Cost | Useful number |
|---|---|---|
| Fat-derived MSCs, first treatment at one site | ¥1,100,000 | Base price in one MHLW-published plan |
| Same plan, two treatment sites | ¥1,650,000 | ¥550,000 less than paying ¥1.1 million twice |
| Same plan, later treatment | ¥550,000 | 50% of the first one-site treatment fee |
| Another fat-derived MSC plan | ¥1,815,000 | ¥715,000 more than the ¥1.1 million example |
| Synovial stem cells, one knee | ¥2,800,000 | Different cells and treatment process |
| Culture period in one fat-derived MSC plan | 4–5 weeks | About 28–35 days between collection and injection |
Under the ¥1.1 million plan, treating two sites costs ¥1.65 million. That is ¥550,000, or 25%, less than paying ¥1.1 million twice. A later treatment costs ¥550,000, which is 50% of the first one-site treatment fee.[1]
The ¥1.815 million and ¥2.8 million prices should not be used to rank treatment quality. The first is a fat-derived stem cell plan. The ¥2.8 million treatment uses synovial stem cells collected from the knee and follows a different process.[2][3]
What the Quote Should Cover
The ¥1.1 million treatment plan includes cell processing, stem cell administration, tests, medicines and related supplies. Its first treatment costs ¥1.1 million for one site and ¥1.65 million for two sites. Treatment from the second administration onward is ¥550,000.[1]
The ¥1.815 million plan is also self-pay. Travel and transport are paid separately. If treatment stops after examination, testing, fat collection, transport or cell processing has already taken place, the patient may still have to pay those costs.[2]
The ¥2.8 million synovial stem cell plan includes consultation, blood collection for autologous serum, synovial tissue collection and the stem cell injection. The blood test immediately before injection is separate. The three- and six-month visits also cost extra.[3]
| Cost item | What to confirm |
|---|---|
| Consultation | Is the first orthopedic assessment included? |
| Imaging | Are X-rays, MRI or other scans separate? |
| Blood tests | Are infection screening and pre-treatment tests included? |
| Tissue collection | Is fat or synovial tissue collection included? |
| Cell processing | Does the price include culture and quality testing? |
| Injection | Is the quote for one knee, one site or one injection? |
| Storage | Will stored cells create another charge? |
| Repeat treatment | What will another injection cost? |
| Follow-up | Which visits and tests are included? |
| Overseas patient costs | Are travel, interpretation and coordination separate? |
A written, itemized quote is one of the basic checks when choosing a stem cell hospital in Japan.
Why Treatment Takes 4–5 Weeks
One MHLW-published fat-derived MSC plan collects about 20 cc, or roughly 10 g, of fat through an incision of about 5 mm. Fat collection takes about 30 minutes. Around 60 mL of blood is also collected.[1]
The collected cells are grown for about one month. Injection takes place around 4–5 weeks, or roughly 28–35 days, after collection. The injection itself takes around 15–30 minutes.[1]
Patients coming from overseas therefore need to plan around the culture period, not just the injection date. The collection, culture and administration steps are also covered in the stem cell treatment process in Japan.
What the Lab Is Charging For
Cultured cells are separated from the collected tissue, grown to the planned amount and checked before they are used. One MHLW plan says the cells are cultured for about one month. Treatment can be stopped if contamination is found, the cells look abnormal or they do not grow to the required number.[1]
- Which facility processes the cells?
- How long will culture take?
- What checks are completed before the cells can be used?
- What happens if contamination is found?
- What happens if too few cells grow?
- What costs remain if no injection is given?
These checks are part of the practical role of a CPC cell processing center in Japan.
What You Can Lose If Treatment Stops
Under the ¥1.1 million plan, stopping treatment within seven days after tissue collection results in a charge of 50% of the treatment cost. After that point, the full treatment amount is payable. If poor cell quality prevents treatment, the plan says another tissue collection and culture can be performed without another treatment charge, although travel remains the patient’s responsibility.[1]
The ¥2.8 million synovial stem cell plan sets out the financial risk more clearly:
| Situation | Cost | Share of ¥2.8 million treatment price |
|---|---|---|
| Cancellation after blood collection but before synovial tissue collection | ¥330,000 | About 12% |
| Cancellation after synovial tissue collection | ¥2,000,000 | About 71% |
| Cells do not grow enough for injection | ¥660,000 | About 24% |
The percentages are simple calculations based on the published ¥2.8 million treatment price. They apply to this plan, not to every Japanese clinic.[3]
Before tissue collection, get the cancellation amount for each stage in writing. The financial difference between stopping before and after collection can exceed ¥1 million.
More Cells Do Not Mean Better Results
A larger cell number can cost more. Research has not shown that doubling the number of cells doubles pain relief or knee function.
The 2025 Cochrane review found large differences between studies in cell source, preparation method and dose. The best preparation and dose are still uncertain.[4]
The ADIPOA2 randomized phase 2b trial compared single injections of 2 million and 10 million autologous fat-derived stromal cells with saline placebo in people with mild-to-moderate knee osteoarthritis. Neither cell dose showed a significant advantage over placebo for the study’s main pain and function outcome.[5]
If a higher-priced plan is mainly sold on cell count, ask what human study supports that dose for your knee.
What Patients Improved by in Trials
The 2025 Cochrane review included 25 randomized trials and 1,341 participants. Eight placebo-controlled trials included 459 participants.[4]
| Outcome | Placebo | Stem cell group | What the review found |
|---|---|---|---|
| Pain at about 6 months, 0–10 scale | 4.5 | 3.3 | 1.2 points better; low-certainty evidence |
| Function at about 6 months, 0–100 scale | 46.3 | 32.1 | 14.2 points better; low-certainty evidence |
| Reported treatment success | 530 per 1,000 | 683 per 1,000 | Very low-certainty evidence |
| Serious adverse events | 23 per 1,000 | 16 per 1,000 | Too uncertain to show a reliable safety difference |
The pain estimate came from 7 studies with 445 participants. The function estimate came from 7 studies with 432 participants. The serious-adverse-event analysis included 461 participants.[4]
These are group averages. They are not a personal prediction. The figure of 683 per 1,000 should also not be advertised as a general 68.3% success rate because Cochrane rated that result as very uncertain.
ADIPOA2 did not find a significant advantage over placebo for its main pain and function outcome.[5] The evidence therefore includes both positive average results and trials that did not show a clear benefit.
The clinical data are examined by treatment type in our knee osteoarthritis and regenerative medicine in Japan review.
How Long the Benefit Is Known to Last
Cochrane found possible small improvements in pain and function at up to about six months. Some studies reported treatment success later, but the certainty of the longer-term evidence was very low.[4]
There is no reliable single number such as “one injection lasts two years” that applies to all cell types, doses and patients.
For a patient paying ¥1.1 million, duration directly affects value. A later treatment in the same published plan costs another ¥550,000. Ask what follow-up data support any claimed treatment duration before using that claim to judge the price.
Pain Relief Is Not Cartilage Regrowth
Current evidence does not show that knee stem cell injections reliably regrow lost cartilage.
The Cochrane review found that structural disease progression was not assessed in the trials used for this outcome. Whether stem cell injections change the underlying progression of knee osteoarthritis remains uncertain.[4]
A patient can have less pain without proving that cartilage has grown back. Before-and-after MRI images should therefore be considered together with walking ability, pain and knee function rather than used alone as proof of treatment success.
What Insurance Covers
The three stem cell plans used in the main price comparison are self-pay. The MHLW documents state that these treatments are outside public insurance.[1][2][3]
Japan also has JACC autologous cultured cartilage for selected patients. One current MHLW knee osteoarthritis document notes that insurance-covered JACC treatment may be considered depending on the patient’s condition.[2]
JACC is not the same treatment as an injection of cultured fat-derived MSCs. It uses cultured cartilage and follows a different treatment process. Insurance coverage for JACC therefore does not make the private stem cell plans above insured treatments.
What “Registered in Japan” Actually Means
Japan has a legal process for providing regenerative medicine. Depending on the risk class, the treatment must go through the required committee review and treatment-plan process. Providing covered regenerative medicine without the required plan can violate the law.[6]
A filed treatment plan does not mean the government has guaranteed that the treatment will work. A regenerative medicine provision plan, regulatory product approval and public insurance coverage are separate things.
The difference between these routes is covered in the Japan regenerative medicine registration and compliance guide.
What Can Go Wrong
| Part of treatment | Possible problem |
|---|---|
| Fat or tissue collection | Pain, bruising, bleeding, swelling, infection or problems related to local anesthesia |
| Cell culture | Contamination, abnormal cells or inadequate cell growth may stop treatment |
| Knee injection | Temporary pain or swelling; invasive joint procedures also carry an infection risk |
| Treatment result | The procedure may be completed safely but provide little or no useful improvement |
The MHLW-published fat-derived MSC document lists bleeding, pain, swelling, infection and other complications linked to tissue collection. It also states that treatment can stop if the cells are contaminated, look abnormal or fail to grow to the planned number.[1]
The same document records one reported death in Japan from pulmonary embolism after intravenous administration of autologous fat-derived MSCs. It states that the direct relationship between the treatment and death was unclear.[1] This involved intravenous treatment, not a knee injection, so it should not be used as the estimated risk of an intra-articular knee procedure.
Cochrane found 4 serious adverse events among 242 stem-cell recipients and 5 among 219 placebo recipients. The numbers were too small to establish a reliable difference in safety.[4]
The American Academy of Orthopaedic Surgeons also states that strong evidence for stem cell treatment in orthopedic conditions is still lacking and that invasive procedures can carry risks such as infection.[7]
The same issues are covered from the patient-safety side in Is Stem Cell Therapy Safe in Japan?
When the Diagnosis Fits the Treatment
The evidence in this article is mainly about knee osteoarthritis. It should not automatically be applied to meniscus tears, ligament injuries, inflammatory arthritis or every other cause of knee pain.
Before paying for treatment, the doctor should establish:
- whether knee osteoarthritis is actually causing the pain;
- how advanced the joint damage is;
- where the damage is located;
- whether leg alignment is increasing pressure on the knee;
- whether the meniscus or ligaments are also involved;
- which conservative treatments have already been tried;
- whether another orthopedic treatment is more suitable.
NIAMS notes that osteoarthritis assessment can involve medical history, physical examination, imaging and, when necessary, laboratory or joint-fluid testing to rule out other causes.[8]
Infection status, allergies and other health conditions can also affect whether a specific treatment can go ahead. These screening issues are covered in the stem cell therapy indications and contraindications page.
What to Compare Before Spending ¥1 Million+
A private stem cell treatment should be compared with the other realistic options for the same knee.
NIAMS lists exercise, weight management when appropriate, medicines, physical therapy and surgery among the approaches used for osteoarthritis.[8]
Some patients may still have standard non-surgical options available. Others may have joint damage where surgery deserves serious discussion. Paying more does not make stem cell treatment the better choice automatically.
Ask the doctor:
“What extra benefit do you realistically expect from this stem cell treatment compared with the other options still available for my knee?”
The answer should be based on your diagnosis, imaging, pain, function and previous treatment—not only on the fact that stem cell therapy is available.
Two Trips or a 4–5 Week Stay
One MHLW-published plan separates fat collection and stem cell injection by 4–5 weeks, or about 28–35 days. Follow-up is scheduled at 1, 3 and 6 months after treatment.[1]
Another MHLW plan requires follow-up through six months and allows telephone follow-up when regular attendance is difficult.[2]
For an overseas patient, the main choices are:
- Two trips: one trip for tissue collection and another around one month later for the injection.
- Long stay: remain in Japan during the cell-culture period and avoid a second international flight.
Before booking travel, confirm:
- how many in-person visits are required;
- the planned injection date;
- whether your existing MRI can be used;
- which blood tests need to be repeated in Japan;
- whether follow-up can be completed after returning home;
- what happens if cell growth delays the injection;
- whether interpretation or coordination is charged separately.
These costs and scheduling issues are covered in the medical travel guide for stem cell treatment in Japan.
Questions to Get Answered in Writing
| Question | Why it matters |
|---|---|
| What is my exact knee diagnosis? | The evidence needs to match the real cause of the pain. |
| What type of cells will be used? | Fat-derived MSCs and synovial stem cells are different treatments. |
| What is the full price? | Tests, collection, culture, injection and follow-up may not all be included. |
| Is the price for one knee, one site or one injection? | These terms can change the final cost. |
| Is another injection already expected? | One published plan charges another ¥550,000 for later treatment. |
| What happens if the cells do not grow? | Some plans still leave substantial processing costs payable. |
| What is the cancellation policy? | One published ¥2.8 million plan can leave a ¥2 million charge after tissue collection. |
| How long is the culture period? | One published plan requires about 28–35 days. |
| What result should I realistically expect? | Research gives group averages, not a guaranteed personal result. |
| How will the result be measured? | Pain and function should be compared with a clear starting point. |
| What is the treatment’s regulatory status? | A submitted treatment plan and an approved product are not the same thing. |
Finally
Current MHLW records put the three private knee stem cell examples in this article at ¥1.1 million, ¥1.815 million and ¥2.8 million. Under the ¥1.1 million plan, two treatment sites cost ¥1.65 million and later treatment costs ¥550,000. One culture process takes 28–35 days, while cancellation after tissue collection can leave a charge as high as ¥2 million in the ¥2.8 million plan. The medical result is less certain than the price: Cochrane found low-certainty evidence of small average improvements in pain and function at about six months. Get the diagnosis, total cost, cancellation rules, cell type, expected result and follow-up schedule in writing before paying.