On this page
- Why cartilage does not repair itself
- Repair tissue is not the same tissue
- What the research literature covers
- How structural change is measured, and why it is hard
- Symptom change without structural change
- Focal defects versus generalised disease
- What would count as demonstrated regeneration
- Reading a regeneration claim
- Frequently asked questions
- Requesting a medical evaluation
The promise of rebuilt cartilage is the most commercially useful claim in this field and the least supported. Cartilage regeneration research is worth reading carefully, because the gap between what the studies measure and what the marketing claims is wider here than almost anywhere else on this site.
Why cartilage does not repair itself
Articular cartilage has no blood supply, no nerves and no lymphatic drainage. The cells within it, chondrocytes, are sparse and embedded in a dense matrix they produce themselves.
Without blood, the normal repair sequence cannot run. There is no inflammatory phase delivering cells and signals to the site, because nothing can get there.
Chondrocytes divide very little in adult tissue. A defect therefore stays a defect, and this is why cartilage injury is a permanent problem in a way that a muscle tear is not.
That biology is exactly why the idea of injecting cells to repair it is appealing — and why it is harder than it sounds. The same absence of blood supply that prevents natural repair also means anything injected arrives in a place with no circulation to sustain it.
Repair tissue is not the same tissue
Where repair does occur — after microfracture, or spontaneously at the edge of a defect — what forms is usually fibrocartilage, dominated by type I collagen.
Native articular cartilage is hyaline, dominated by type II collagen in a highly organised architecture that gives it its mechanical properties.
Fibrocartilage works, up to a point, and tends to deteriorate over years under load. A study reporting “defect fill” has not necessarily reported hyaline cartilage, and the distinction requires biopsy to settle.
Any claim of repair that has not looked at what the tissue actually is, is a claim about an appearance on a scan.
This is the single most useful thing to understand before reading any clinic page on the subject. Filling a defect and restoring a joint surface are different achievements, and only one of them is what patients think they are buying.
What the research literature covers
A review has examined what the laboratory and early clinical work supports — Stem cells in articular cartilage regeneration.
A 2025 prospective randomised study looked specifically at cartilage regeneration potential in early knee osteoarthritis — Cartilage Regeneration Potential in Early Osteoarthritis of the Knee: A Prospective, Randomized study.
Cultured bone marrow-derived cells have been used in knees with cartilage defects — Injectable cultured bone marrow-derived mesenchymal stem cells in varus knees with cartilage defects.
And the central question has been asked directly in a review — Biologic injections for osteoarthritis and articular cartilage damage: can we modify disease? — where “can we modify disease” is precisely the structural question rather than the symptomatic one.
How structural change is measured, and why it is hard
MRI can estimate cartilage thickness and volume, and specialised sequences can assess composition. It is non-invasive and its resolution limits what can be detected.
Second-look arthroscopy visualises the surface directly and is invasive. Biopsy tells you what the tissue actually is and is more invasive still, which is why so few studies do it.
The measurement problem compounds the evidence problem: the studies most able to demonstrate regeneration are the ones patients are least willing to join.
Meanwhile a pain questionnaire costs nothing and can be administered by post, which is part of why symptom endpoints dominate.
None of which is dishonest on the researchers’ part. They measure what is feasible and state clearly what they measured. The distortion happens downstream, when a symptom result is described as tissue repair.
Symptom change without structural change
Several trials report improved pain and function with no demonstrated change in cartilage. That is a real and useful result, and it is not regeneration.
It is also biologically coherent. Cartilage has no nerves, so cartilage damage does not itself hurt. Pain in osteoarthritis comes from bone, synovium and surrounding soft tissue — all of which an anti-inflammatory effect could plausibly influence without touching the cartilage at all.
So a treatment can work, in the sense that matters to a patient, while the regeneration story is entirely wrong — see MSC immunomodulation.
Focal defects versus generalised disease
A discrete hole in an otherwise sound surface is a more tractable target than diffuse thinning across a whole joint. There is a defined area to fill and healthy tissue around it.
That is where the surgical cartilage procedures — microfracture, osteochondral transfer, chondrocyte implantation — have their evidence, and where cell-based approaches are most plausible.
Generalised osteoarthritis is a different problem, and evidence from one does not transfer cleanly to the other — see cartilage damage and osteoarthritis.
What would count as demonstrated regeneration
Imaging showing increased cartilage thickness at the defect, sustained beyond two years.
Biopsy confirming hyaline rather than fibrocartilage, with appropriate collagen composition and architecture.
And function maintained over years, because repair tissue that degrades under load has delayed a problem rather than solved one.
Very few studies meet the first two together. None on the scale that would settle the question — see the limits of current evidence.
Reading a regeneration claim
Ask what was measured — a symptom score, an image, or tissue. Ask over how long. Ask whether there was a comparison group.
Ask specifically whether hyaline cartilage was demonstrated, and by what method. The answer is usually that it was not looked for.
That does not make the treatment worthless. It makes repair the wrong word for it, and symptom relief the right one — see the research library.
Frequently asked questions
Can stem cells regrow cartilage?
Not demonstrated. Most trials measure symptoms rather than tissue, and where repair tissue forms it is usually fibrocartilage rather than the original hyaline type.
What is the difference between fibrocartilage and hyaline?
Hyaline is the original articular surface, mechanically superior and highly organised. Fibrocartilage is scar-like repair tissue that tends to deteriorate under load.
Why does cartilage not heal on its own?
No blood supply, so the normal repair sequence cannot run, and adult chondrocytes divide very little.
If my pain improves, has the cartilage healed?
Not necessarily. Cartilage has no nerves — osteoarthritis pain comes from bone and surrounding tissue, which an anti-inflammatory effect could influence without changing cartilage.
How would anyone prove regeneration?
Imaging showing sustained thickness increase plus biopsy confirming hyaline tissue, held over years. Very few studies do both.
Is a focal defect different from arthritis?
Yes, and more tractable — a defined area to fill with healthy tissue around it. Evidence does not transfer cleanly between the two.
Requesting a medical evaluation
Nothing on this page establishes whether any treatment is appropriate for you. That needs your history, your imaging and your current medications read by a clinician. If you would like that review, send your records and we will tell you honestly whether there is anything worth discussing — including when the answer is no.
This page is general information, not medical advice, and does not create a doctor–patient relationship. Regenerative treatments discussed here are in most cases investigational. Discuss any treatment with a clinician who knows your history.