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What Is Autologous Chondrocyte Implantation?

Autologous chondrocyte implantation is a cartilage-restoration procedure that uses a patient's own cartilage cells to repair a focal articular cartilage defect. The procedure is generally performed in two stages, beginning with arthroscopic collection of a small cartilage sample from a low-load area of the knee. Chondrocytes from that sample are expanded in a laboratory and later implanted into the prepared defect. Matrix-assisted versions place the cultured cells on a scaffold that is trimmed to fit the damaged area.

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What Is Autologous Chondrocyte Implantation?

Autologous chondrocyte implantation is a cartilage-restoration procedure that uses a patient's own cartilage cells to repair a focal articular cartilage defect. The procedure is generally performed in two stages, beginning with arthroscopic collection of a small cartilage sample from a low-load area of the knee. Chondrocytes from that sample are expanded in a laboratory and later implanted into the prepared defect. Matrix-assisted versions place the cultured cells on a scaffold that is trimmed to fit the damaged area.

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Why Is Autologous Chondrocyte Implantation Performed?

The procedure is used for symptomatic focal full-thickness cartilage defects of the knee in carefully selected patients. It is generally considered when the surrounding joint is otherwise suitable for cartilage restoration and symptoms persist despite nonsurgical care. Surgeons assess defect size and location, alignment, ligament stability, meniscal status, age, activity level, and the amount of generalized osteoarthritis before recommending treatment. Malalignment, instability, or meniscal deficiency can require correction at the same time to protect the implanted cartilage.

How Is Autologous Chondrocyte Implantation Performed?

The first stage uses arthroscopy to inspect the knee and harvest a small sample of healthy cartilage for cell culture. After the chondrocytes have been expanded, a second operation exposes and debrides the cartilage defect to stable healthy margins. The cultured cells are then placed into the defect, either beneath a covering membrane or on a cell-seeded scaffold such as a matrix-assisted implant. The implant is secured to the prepared defect, and any planned alignment, ligament, or meniscal procedure can be performed during the same operation.

What Is Recovery Like After Autologous Chondrocyte Implantation?

Recovery is deliberately gradual because the implanted cells and repair tissue need time to mature. Weight-bearing is restricted or progressed slowly according to defect location, size, fixation, and associated procedures. Physical therapy emphasizes controlled range of motion first, followed by progressive strength, gait, and higher-level activity. Return to running, jumping, and pivoting sports generally takes many months and depends on symptoms, strength, imaging, and the surgeon's rehabilitation protocol.

What Are the Risks and Complications?

Possible complications include infection, blood clots, stiffness, persistent pain, graft delamination, graft hypertrophy, and incomplete cartilage repair. Scar tissue or overgrowth at the implant site can cause catching or require arthroscopic treatment. The repair can fail when abnormal alignment, instability, meniscal loss, or progressive osteoarthritis continues to overload the treated area. Additional cartilage surgery or another knee procedure can be required if symptoms persist or the graft fails.

Frequently Asked Questions About Autologous Chondrocyte Implantation

Why are two operations commonly needed for autologous chondrocyte implantation?

The first operation collects cartilage cells for laboratory expansion. The second operation places the cultured cells into the prepared cartilage defect after enough cells have been produced.

Is MACI a form of autologous chondrocyte implantation?

Yes. Matrix-induced autologous chondrocyte implantation uses a scaffold seeded with the patient's cultured chondrocytes and is one modern form of ACI.

Is ACI used for generalized knee arthritis?

It is mainly intended for focal cartilage defects rather than diffuse advanced osteoarthritis. Generalized joint degeneration can make cartilage restoration less likely to succeed.

Can other knee procedures be done with ACI?

Yes. Alignment correction, ligament reconstruction, or meniscal treatment can be combined with ACI when those problems would otherwise overload the repaired cartilage.

References

Articular Cartilage Restoration. OrthoInfo, American Academy of Orthopaedic Surgeons. https://orthoinfo.aaos.org/en/treatment/articular-cartilage-restoration/. Date Accessed August 13, 2026.

MACI (autologous cultured chondrocytes on porcine collagen membrane). U.S. Food and Drug Administration. https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/maci-autologous-cultured-chondrocytes-porcine-collagen-membrane. Date Accessed August 13, 2026.

Latest Advances in Chondrocyte-Based Cartilage Repair. PubMed Central (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC11201646/. Date Accessed August 13, 2026.

Failures, re-operations, and complications after autologous chondrocyte implantation ? a systematic review. PubMed. https://pubmed.ncbi.nlm.nih.gov/21333744/. Date Accessed August 13, 2026.

The Most Common Rehabilitation Protocol After Matrix-Assisted Autologous Chondrocyte Implantation Is Immediate Partial Weight-Bearing and Continuous Passive Motion. PubMed Central (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC9791827/. Date Accessed August 13, 2026.