The Coral Knee Implant (CartiHeal Agili-C): What I Tell Patients

Patients ask me about the coral knee implant more and more, usually after reading that it can regrow cartilage. It’s a real device, and it does have a role, but that role is much narrower than most of what’s written about it. Here’s what it is, who it’s for, and how I think about it.

What the coral implant is

The coral implant is CartiHeal Agili-C, now made by Smith+Nephew. It’s a small cylinder made from aragonite, the mineral that coral is built from. During knee surgery, a hole is made in the bone under a damaged spot of cartilage, and the implant is pressed into it. It works as a scaffold: your own tissue grows into it over time.

The FDA approved it in March 2022. It isn’t an injection. It’s surgery, followed by a period of rehab.

Who it’s designed for

It’s approved for damaged areas of knee cartilage, in knees that don’t have severe arthritis. Think of a pothole in an otherwise good road. The implant fills the pothole. It doesn’t repave the road.

Most people who ask me about it don’t have a pothole. They have arthritis: cartilage worn across the joint, often with the leg shifting out of line, bone spurs, and pain that has built up over years.

My concerns

Here’s what I weigh when a patient asks me about it.

• Arthritis is more than a damaged spot. As I explain in can you regrow cartilage in your knee or hip?, arthritis involves alignment, a limited blood supply, the cartilage itself, and outside factors like inflammation and family history. A plug in one spot doesn’t address the rest.
• It’s still surgery. It comes with an operation and a rehab period, for a treatment that only suits a narrow group of knees.
• The patients it suits usually do well without it. A younger patient with one damaged spot and a healthy knee otherwise usually does well without surgery, and that’s how I treat them first.

What I usually recommend first

For knee arthritis, I follow a step-by-step plan, moving on only when a step stops working:

1. Start simple: physical therapy, medication, and a brace.
2. Then injections: cortisone, gel, or PRP.
3. Then replacement, when the knee still limits your life: a partial or total knee replacement, both with decades of results behind them.

For my take on the other options you may be reading about, from the knee spring to artery embolization, see alternatives to knee replacement.

Insurance and cost

Insurance coverage for the coral implant has been limited. A new billing code for the procedure takes effect in January 2027, which may help, but check with your plan before assuming it’s covered. The treatments above are generally covered, except PRP, which is an out-of-pocket cost.

I see patients in Washington, D.C. and Germantown, Maryland. Request an appointment.

This article is general education and reflects my professional opinion. It isn’t advice about your specific knee.