Do stem cells regenerate the joint?

What this is

Clinics inject preparations described as stem cells into the knee and often sell a repair story. The evidence question is what happens to pain, function, and the joint itself compared with placebo.

It isn't PRP. PRP's debate is a possible benefit versus placebo alongside a guideline split. Stem-cell injections have a small, low-certainty pain and function finding, no established joint repair, and a rheumatology guideline that recommends against them.

What the evidence shows

A living Cochrane review found that, versus placebo, pain and function may improve slightly for up to six months. Certainty is low: products differ, and some larger trials were withdrawn without reporting results, leaving the evidence base smaller and less certain than it otherwise might have been.

Quality of life and whether people felt the treatment “worked” are even less certain.

Regeneration is not established

The reason many people pay for this is cartilage repair. That claim is not established. The review did not assess imaging change over time in a way that would support it.

That isn't the same as saying a definitive imaging trial failed. It means the regeneration promise hasn't been shown.

What taking part usually involves

• A clinic procedure, often expensive and often out of pocket.
• Products that may not match one another, or match what little was studied.
• Follow-up that should ask about pain and function, not assume the joint was rebuilt.

What this does not do

Stem cell injections haven't been shown to regenerate the joint, replace a disease-modifying drug, or stand in for PRP. A living review can be updated. That isn't a promise that proof is around the corner.