Stem Cells for Knee Osteoarthritis: What a Clinical Trial Found

A 2025 Phase I trial tested placental-derived stem cells for knee osteoarthritis. Patients reported real pain relief lasting 12 months. Here’s what happened.

Tired of Knee Pain That Won’t Go Away?

If you’ve tried painkillers, physiotherapy, and injections but your knee still aches, you’re not alone. Hundreds of millions of people worldwide live with knee osteoarthritis — and most current treatments only manage the pain rather than address its root cause.

That’s exactly why researchers are looking at stem cells as a potential next step. In April 2025, a clinical trial from the National Academy of Medical Sciences of Ukraine published results testing whether stem cell injections could offer real, lasting relief for people with knee osteoarthritis. Here’s what they found — in plain language.

What Is Knee Osteoarthritis?

Knee osteoarthritis happens when the cartilage cushioning your knee joint gradually wears down. Once it’s gone, bone rubs on bone — causing pain, stiffness, and difficulty moving. It affects people of all ages, though it becomes more common with age, obesity, or a history of high-impact physical activity.

The World Health Organization estimates 380 million people globally are affected. Despite how common it is, none of today’s standard treatments — anti-inflammatory drugs, hyaluronic acid injections, or even surgery — can actually rebuild lost cartilage. They help manage symptoms, but they don’t fix the underlying damage.

Why Stem Cells?

Stem cells are special because they can transform into different types of tissue — including cartilage cells. More importantly, they also have natural anti-inflammatory properties, meaning they can help calm the damaged joint environment rather than just masking the pain.

The type used in this trial were mesenchymal stem cells (MSCs) derived from human placental tissue — collected after birth with donor consent, ethically sourced, and stored frozen until needed. These cells have shown promising results in earlier laboratory and animal studies, which is why researchers moved forward with a human trial.

How Was the Trial Conducted?

The study enrolled 26 patients with moderate to moderately advanced knee osteoarthritis — 9 men and 17 women, aged between 23 and 74. They were split into two groups:

The stem cell group (15 patients) received three injections directly into the knee joint, each containing 20 million stem cells, on top of standard hyaluronic acid treatment. Total dose: 60 million cells over three sessions.

The control group (11 patients) received three hyaluronic acid injections only — the conventional approach.

Both groups followed the same schedule: one injection every four weeks. Patients were then monitored at 6 months and 12 months using pain scores, function questionnaires, MRI scans, and blood tests.

Was It Safe?

This was the trial’s primary question — and the answer was broadly yes, with some caveats.

After the first injection, 73% of stem cell patients reported temporary joint pain and about 27% experienced swelling. By comparison, only around 12.5% of the control group reported discomfort.

The important detail: all side effects cleared up on their own within 3 to 7 days. No one experienced a serious reaction. No medical intervention was needed beyond the normal monitoring schedule. By the two-week check-up after each injection, both groups were doing fine.

The temporary discomfort is thought to reflect the stem cells actively interacting with the joint — a normal biological response rather than a danger sign.

Did Patients Actually Feel Better?

Yes — and the improvement lasted.

The stem cell group showed significant reductions in both pain and physical function scores at 6 months, and those improvements were still present at the 12-month mark. The control group receiving only hyaluronic acid did not show the same level of improvement over the same period.

MRI scans at 12 months did not show measurable cartilage regrowth in either group — which is an honest and expected finding for a one-year study. Structural tissue changes may simply take longer to appear, and future studies with longer follow-up will need to explore this.

Blood tests also revealed an interesting result: a specific immune marker called IL-2 dropped significantly in the stem cell group. This aligns with what researchers know about stem cells’ ability to regulate inflammation — and may partly explain why patients felt better.

What Does This All Mean?

This was a Phase I trial — meaning it was designed primarily to test safety, not to deliver a final verdict. With only 26 patients, it’s a first step, not a conclusion. But it’s a well-structured, peer-reviewed step that adds to the growing global body of research on stem cells for joint conditions.

The key takeaways are straightforward:

The treatment was safe — side effects were manageable and short-lived. Patients in the stem cell group reported real, sustained improvements in pain and function lasting at least one year. Cartilage regrowth wasn’t visible on MRI within 12 months, but larger and longer trials are needed to fully understand that question.

Regulatory agencies around the world — including the FDA, the European Medicines Agency, and others across Asia and Latin America — are actively developing frameworks for stem cell therapies. Studies like this one help build the evidence base that responsible regulation depends on.

The Bottom Line

For the millions of people living with knee osteoarthritis who feel let down by existing treatments, this trial offers something genuinely worth watching: a safe, stem cell-based approach that appears to deliver lasting pain relief — and a clear pathway for the larger studies that need to follow.

It’s not a cure. It’s not approved for routine use yet. But it’s a meaningful step forward.