RegenSelect · Research Guide

The MILES Trial: What the Research Actually Found

480 patients. A randomized controlled trial. Published in Nature Medicine in 2023. And almost never mentioned on clinic websites. Here's what it found — and what it doesn't mean.

The finding, in plain English

Researchers compared three types of stem cell therapy to a standard corticosteroid injection in 480 patients with knee osteoarthritis. After 12 months, all four groups had improved. But none of the stem cell treatments produced significantly better outcomes than the corticosteroid injection.

In other words: the treatment that costs $300 performed as well, statistically, as the treatments costing $4,000–$12,500.

This doesn't mean stem cell therapy doesn't work. It means the evidence that it works better — at the 12-month mark, in the patient population studied — isn't there yet. That's an important distinction. And it's why you deserve to know about this study before spending thousands of dollars.

The study

"Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial"

Mautner K, et al. — Nature Medicine, Vol. 29, pp. 3120–3126. Published November 2, 2023. DOI: 10.1038/s41591-023-02632-w ↗

Study lead: Boden SD, Emory University. Multi-site randomized controlled trial. ClinicalTrials.gov: NCT03818737 ↗

What they actually tested

Patients were randomly assigned to one of four groups and followed for 12 months.

Group 1

Bone marrow aspirate concentrate (BMAC)

Patient's own bone marrow cells

Group 2

Bone marrow concentrate + adipose cells

Patient's own bone marrow + fat cells

Group 3

Adipose-derived cells alone

Patient's own fat tissue

Group 4

Corticosteroid injection

Standard anti-inflammatory injection (the control group)

Groups 1–3 used autologous (patient's own) cells. Group 4 was the corticosteroid control. All injections were image-guided. All patients followed a standardized rehabilitation protocol.

How the study came to exist

2015

Trial design

Researchers at Emory University design a multi-site randomized controlled trial to test whether stem cell therapy outperforms corticosteroid injection for knee osteoarthritis.

2017

Enrollment begins

480 patients with knee OA enrolled across multiple U.S. sites. Patients are randomly assigned to one of four groups.

2019–2021

Treatment and follow-up

Patients receive their assigned treatment and are followed for 12 months. Outcomes measured by standardized pain and function scales.

Nov 2023

Results published

Mautner et al. publish in Nature Medicine. Title: 'Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial.'

What people get wrong about it

The MILES Trial gets cited in two directions — as proof that stem cells are useless, and as something to ignore entirely. Both are wrong.

"Stem cell therapy doesn't work"

Overstated

All four groups improved significantly from baseline. The trial showed that stem cell therapy produces real improvement — it just didn't produce more improvement than corticosteroid at 12 months. That's a different conclusion than 'it doesn't work.'

"Corticosteroids are better than stem cells"

Also overstated

The trial found no statistically significant difference between groups — which means neither treatment was proven superior to the other. Corticosteroids are faster-acting and cheaper, but the data doesn't establish that they produce better outcomes overall.

"Stem cell therapy is a waste of money"

Partially true

If a corticosteroid injection costs $300 and produces equivalent outcomes at 12 months, paying $8,000 for stem cells requires justification beyond that timeframe. The trial only measured 12-month outcomes. Whether stem cell therapy has longer-lasting effects — or whether it slows structural progression — was not tested here.

"The trial proves patients should skip stem cells"

Too simple

Patient selection matters enormously. The MILES Trial enrolled patients with a range of OA severity. The trial did not break down outcomes by Kellgren-Lawrence grade, which means it can't tell us whether patients with grade 2–3 OA (not bone-on-bone) would have responded differently than those with more advanced disease.

What providers argue — and how to evaluate it

Legitimate providers have real counterarguments to the MILES Trial. Here's how to tell a genuine one from a dismissal.

"The trial used older protocols"

Worth considering, with caveats

Some providers argue that the specific products or concentrations used in the MILES Trial don't reflect current best practice. This is a legitimate argument — but it requires the provider to show specifically what their protocol differs in, not just wave the concern away. Ask them to explain the difference precisely.

"12 months isn't long enough"

Reasonable, but speculative

Stem cell therapy proponents argue the biological effect takes longer than 12 months to fully manifest. This may be true — but the claim needs to be supported by actual long-term follow-up data, not just assertion. Ask your provider if they track their own patient outcomes beyond one year.

"Patient selection wasn't strict enough"

The strongest counterargument

The MILES Trial enrolled patients across a wide range of OA severity. Most experienced providers believe stem cell therapy works best in grade 2–3 OA (moderate, not bone-on-bone). If the trial included a large proportion of advanced-grade patients unlikely to respond, the results would be diluted. This is a real methodological concern — but it's the provider's job to select appropriately, not to dismiss the trial wholesale.

The bottom line

The MILES Trial is the best evidence currently available. It doesn't end the conversation — it starts the right one. Any provider who dismisses it without a specific, clinical counterargument is not being straight with you. Any provider who can discuss it clearly, acknowledge its limitations, and explain how their specific protocol and patient selection differs is worth listening to.

Ask every provider you consult: "What is your response to the MILES Trial findings?" The answer will tell you a great deal about how they approach clinical honesty.

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