Knee Cartilage
Demo Author One
Cartilage repair options for lasting joint health
A practical overview of cartilage repair, injection therapy, rehabilitation planning, and the clinical evidence that guides joint preservation care.
Cartilage repair compared
MACI vs microfracture: which cartilage repair is right?
A simpler, cheaper fix for small lesions, or durable hyaline-like cartilage for larger damage — and the modern UK-available step beyond both.
Reviewed byProf Paul Lee MBBch, FRCS (Tr & Orth), PhDLast reviewed 1 May 2026Quick answer
Microfracture is the simpler, cheaper option for small cartilage lesions, but it forms weaker fibrocartilage; MACI grows more durable, hyaline-like cartilage and holds up better for larger defects. For most defects worth treating with cell therapy, the modern UK-available step beyond both is STACi.
Two different ways to repair cartilage
Microfracture is a keyhole technique that has been used for decades. The surgeon makes tiny holes in the bone beneath the damaged cartilage; this releases blood and bone-marrow cells that form a repair tissue over the defect. It is quick, done in a single operation, and comparatively inexpensive. Its limitation is what it grows: the repair is fibrocartilage — a scar-like cartilage that is mechanically weaker and less durable than the original, and which can wear down over time, particularly in larger or high-load areas.
MACi takes a cell-therapy approach. Your own cartilage cells are harvested, grown in a laboratory, seeded onto a collagen membrane and implanted at a second operation. What it aims to grow is hyaline-like cartilage — much closer to the smooth, durable cartilage you were born with. That makes it better suited to larger defects and to durability over time. The trade-offs are that MACi needs two operations, is licensed for the knee only, and — importantly in the UK — is not currently available here as a licensed product.
MACI vs microfracture, side by side
| What to compare | Microfracture | MACI |
|---|---|---|
| Type of repair tissue | Fibrocartilage (scar-like, weaker) | Hyaline-like cartilage (closer to natural) |
| Best defect size | Small lesions | Larger focal defects (up to ~4 cm²) |
| Number of operations | One | Two (biopsy, then implantation) |
| Durability | Can wear over time, especially under load | Aims for more durable, longer-lasting repair |
| Cost | Lower | Higher (cell culture + two operations) |
| Complexity | Simple keyhole technique | Specialist cell-therapy procedure |
| UK availability | Available | Not currently available as a licensed product |
When microfracture makes sense
Microfracture is fair to consider, and sometimes the right call, when the lesion is small, when a single, low-cost, low-complexity procedure is the priority, or as an early-stage option. For small defects it can give good symptom relief, and its simplicity is a genuine advantage.
Its weakness is durability. Because it forms fibrocartilage rather than true hyaline cartilage, the repair can degrade over time — a bigger concern in larger defects, in higher-load areas, and in more active patients who need the repair to last.
When the case points beyond microfracture — and to STACi
Where the defect is larger, where durability matters, or where a previous microfracture has not held up, the argument shifts toward growing proper hyaline-like cartilage — which is what cell therapy does. MACi is one way to do that, but in the UK its availability is the sticking point.
That is why, at London Cartilage Clinic, the route we offer is STACi. STACi delivers your own cartilage cells inside a three-dimensional scaffold rather than on a flat 2D sheet, supporting growth through the depth of the defect. It treats larger and more complex defects than either microfracture or MACi comfortably handle, works across any joint, is most often a single operation, and — unlike MACi — is available in the UK.
Microfracture for the smallest lesions; hyaline-like cell therapy where durability matters — delivered in the UK, in one operation, as STACi.
If you are weighing MACi against the original ACi rather than against microfracture, see ACi vs MACi.
Frequently Asked Questions
Is MACI better than microfracture?
They suit different situations. Microfracture is simpler and cheaper and works for small lesions, but it forms weaker fibrocartilage that can wear over time. MACi grows more durable, hyaline-like cartilage and holds up better for larger defects — at the cost of two operations, and it is not available in the UK.
What is the difference in the cartilage each one grows?
Microfracture produces fibrocartilage — a scar-like, mechanically weaker tissue. MACi produces hyaline-like cartilage, much closer to the smooth, durable cartilage you were born with, which is generally more hard-wearing.
Why does microfracture sometimes fail?
Because the fibrocartilage it forms is weaker and less durable than natural cartilage, the repair can break down over time — particularly in larger defects, high-load areas of the joint, and more active patients. In those cases, cell therapy is often considered next.
If microfracture did not work for me, what are my options?
Growing durable hyaline-like cartilage with cell therapy is the usual next step. MACi is one form of that but is not available in the UK; the UK-available option is STACi, which uses a 3D scaffold, treats larger defects, works in any joint and is usually a single operation.
Can I have MACI instead of microfracture in the UK?
Not as a licensed product — MACi’s EU authorisation was suspended in 2014 and it is now a US, knee-only treatment. If you want cell therapy rather than microfracture, the UK route is an assessment for STACi at London Cartilage Clinic.
How does STACi compare to both?
STACi grows hyaline-like cartilage like MACi, but delivers the cells in a three-dimensional scaffold, treats larger and more complex defects than either microfracture or MACi, works across any joint, is most often a single operation, and is available in the UK.
Still have more specific concerns?
Free Discovery CallNot sure which repair is right for you?
The best choice depends on your defect size, the joint and your goals. Start with a free fifteen-minute discovery call, or book a consultation for Professor Lee to review your imaging and advise.
London Cartilage Clinic
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