Cartilage repair, replacement, and injection options for knee cartilage damage: what patients need to know

Can your knee still be preserved, or is replacement more likely?

Yes — in the right knee, preservation can still be possible, and a replacement is not always the first answer. The usual question is whether the damage is localised enough for a joint-preserving treatment, or whether the whole knee has worn down to the point that replacement is more likely.

That distinction matters because knee cartilage does not heal well on its own. It has very little direct blood supply, so a defect can persist, enlarge, and in some people contribute to osteoarthritis over time. Larger untreated defects are more likely to keep causing symptoms and wear.

Age alone does not decide the treatment. What matters more is the pattern of damage, your symptoms, your activity goals, the alignment of the leg, and whether the rest of the knee is healthy enough to support a repair. For some people, the goal is to reduce pain, improve function, and delay or avoid a replacement for as long as possible. It is important to be realistic, though: preservation does not create a brand-new knee, but it may still offer meaningful improvement in the right patient.

What needs to be checked before choosing a cartilage repair treatment?

A specialist usually needs a full picture of the knee before recommending a repair option. MRI, or magnetic resonance imaging, is commonly used to show the size, depth and location of the cartilage injury, and it can also help look for other problems that may be contributing to pain.

That assessment usually includes the meniscus, the ligaments, the bone beneath the cartilage, the shape and alignment of the leg, and how much arthritis is already present. This matters because cartilage repair often works best when the whole knee problem is addressed, not just the surface defect.

Your symptoms matter too. Where the pain is, whether the knee swells, whether it catches or locks, and how much sport, work or daily activity is limited all help guide the decision. Scans are only part of the answer. The right treatment is usually tailored to both the image and the person.

ACI, MACI and AMIC: what is the difference?

These are all cartilage-restoration procedures, but they are not the same.

Autologous chondrocyte implantation, or ACI, uses your own cartilage cells. A surgeon takes a small sample of cartilage, the cells are grown in a laboratory, and then they are implanted back into the defect later.

MACI, which stands for matrix-induced autologous chondrocyte implantation, is a newer version of that idea. The grown cells are placed on a membrane or scaffold before being implanted. In practice, MACI usually involves two stages: one operation to collect the cells and another to place them back.

AMIC stands for autologous matrix-induced chondrogenesis. It combines microfracture — tiny holes made in the bone to stimulate repair — with a scaffold or membrane that supports the healing tissue. Unlike MACI, it does not use the same cell-culture step.

For patients, the key differences are whether the treatment is usually one stage or two, whether cells are grown in a lab, and how complex the surgery and recovery may be. These procedures are designed for selected cartilage defects, not for every painful arthritic knee.

Is one of these cartilage repair options clearly better?

Not clearly, based on the comparison evidence retrieved here. In the 2025 head-to-head study, MACI, AMIC and arthroscopic minced cartilage implantation all improved pain and function over 2 years.

What that study did not show was a clear winner. Patient-reported outcomes were not significantly different between the groups at 2 years. For patients, that usually means the best option is the one that fits the size and location of the defect, the rest of the knee, the surgeon’s experience, and the practicalities of treatment.

It is also worth being cautious about ranking ACI against MACI and AMIC too confidently, because classic ACI was not strongly represented in the directly retrieved comparison evidence here. So while these are all credible restorative approaches, there is no universal front-runner in this material.

A final point: even when surgery works well, improvement takes time. Rehabilitation is a major part of the result, not an optional extra.

What about injections such as Arthrosamid, PRP, BMAC or MFAT?

These injections may be discussed for knee pain, but they are not all the same and they do not all aim to do the same job. Some are mainly used to ease symptoms, some are marketed as biologic support, and none should automatically be assumed to rebuild cartilage in the way a restorative operation tries to.

In practice, they are usually considered alongside — rather than as direct substitutes for — cartilage repair surgery. If you are thinking about an injection, the most useful question is what problem it is meant to treat:

• pain from osteoarthritis
• a focal cartilage defect
• inflammation in the joint
• a broader mechanical problem in the knee

A careful discussion should also cover expected benefit, how long any benefit might last, whether there is evidence for your specific diagnosis, the likely cost, and whether the injection is being used to delay a more definitive treatment. For Arthrosamid, PRP, BMAC and MFAT specifically, the evidence in this summary is not strong enough to rank them for cartilage damage, so it is sensible to be cautious about any claim that one is clearly best.

Questions to ask at your appointment and what to expect next

The most useful question is: is this a focal cartilage defect, early arthritis, or advanced arthritis? The answer changes the whole treatment pathway.

You can also ask:

• Am I a candidate for preservation, repair, an injection approach, or replacement?
• If I have surgery, how long is recovery likely to take?
• What rehabilitation will I need?
• When could I return to work or sport?
• Are there other problems, such as alignment, meniscus damage, or instability, that also need treatment?

The right plan depends on the exact pattern of damage and the rest of the knee, not just the name of a procedure. If you go to your appointment with those questions, you are more likely to leave with a clear plan and realistic expectations.