Cartilage repair surgery fits one small damaged area

Microfracture surgery makes scar-like cartilage over one spot

During microfracture surgery, a surgeon makes small holes in bone under missing cartilage. Blood and marrow fill the area and form repair tissue as it heals.

The new tissue isn't smooth like the cartilage that covered the bone before. It's tough and scar-like, so it may wear sooner after a demanding recovery.

This operation won't suit arthritis spread over a wide area. It may suit one small bare spot in a knee that's otherwise sound.

ACI and MACI use your own cartilage cells in a later operation

Autologous chondrocyte implantation, or ACI, is an operation using your own cartilage cells. A surgeon removes a small sample, and a laboratory grows more cells.

Matrix-assisted autologous chondrocyte implantation, or MACI, puts those cells on a thin collagen sheet. During the second operation, the surgeon trims that sheet and secures it over the bare spot.

MACI is for a full-thickness defect, meaning cartilage is gone down to bone in one area. Federal regulators licensed that narrow use in adults, but licensing doesn't promise every knee will improve.

Recovery and the rest of the knee decide whether surgery fits

You'll sometimes need a brace, less standing, and months of rehabilitation after repair. Driving, stairs, work, and help at home can't be left until surgery day.

An X-ray shows whether the leg bones line up, while the exam checks whether the knee stays steady. Ask when chores can resume and what the surgeon counts as a poor result.

It won't hurt to ask about care without an operation first. QC Kinetix can explain platelet-rich plasma, or PRP; staff take blood from your arm, separate a platelet-heavy portion by spinning, and guide that material into the sore joint with the aim of easing soreness.

Sources

1. MACI (autologous cultured chondrocytes on a porcine collagen membrane, Vericel; STN BL 125603) IS an FDA-LICENSED cell therapy - and its approved indication is narrow and specific: repair of symptomatic, single or multiple FULL-THICKNESS cartilage defects OF THE KNEE, with or without bone involvement, in adults. It is not approved for osteoarthritis. The existence of one licensed cartilage cell therapy for focal defects is the sharpest available way to show what a licensed 'regeneration' product actually looks like, and how far it is from an injection for a worn joint.

   US Food and Drug Administration, Center for Biologics Evaluation and Research — MACI (autologous cultured chondrocytes on porcine collagen membrane). FDA, 2024.

2. The SUMMIT randomized trial treated 144 patients (mean age 33.8, mean lesion 4.8 cm2) with at least one symptomatic focal cartilage defect (Outerbridge III/IV, >=3 cm2) of the femoral condyle or trochlea. Matrix-applied characterized autologous cultured chondrocytes (MACI) improved KOOS pain (37.0 to 82.5) and function significantly more than microfracture (pain 35.5 to 70.9) at 2 years, with histological and MRI assessment of the repair tissue. This is what a positive cartilage-repair trial looks like - in young patients with a discrete hole, not a worn joint.

   Saris D, et al. — Matrix-Applied Characterized Autologous Cultured Chondrocytes Versus Microfracture: Two-Year Follow-up of a Prospective Randomized Trial.. The American journal of sports medicine, 2014. DOI: 10.1177/0363546514528093.

3. Eighty patients with a single symptomatic chronic femoral condyle cartilage defect were randomized to autologous chondrocyte implantation or microfracture and followed 14-15 years. No significant difference in clinical scores emerged at long-term follow-up; there were 17 failures in the ACI group versus 13 in the microfracture group and more total knee replacements after ACI (6 versus 3). Fifty-seven percent of surviving ACI patients and 48% of surviving microfracture patients had radiographic early osteoarthritis (KL >=2).

   Knutsen G, et al. — A Randomized Multicenter Trial Comparing Autologous Chondrocyte Implantation with Microfracture: Long-Term Follow-up at 14 to 15 Years.. The Journal of bone and joint surgery. American volume, 2016. DOI: 10.2106/JBJS.15.01208.

4. FDA's public list of licensed cellular and gene therapy products is the checkable answer to 'is this FDA-approved?'. A product not on that list, and not being administered under an active IND, is not an approved therapy however it is described in a brochure. For orthopedics the list is short and its cartilage entry is MACI, indicated for focal full-thickness knee defects.

   US Food and Drug Administration, Center for Biologics Evaluation and Research — Approved Cellular and Gene Therapy Products. FDA, 2026.

5. The AAOS clinical practice guideline summary on SURGICAL management of knee osteoarthritis - the other end of the ladder, and the honest comparator for anyone told a biologic injection will let them avoid an operation.

   Srivastava AK, et al. — American Academy of Orthopaedic Surgeons Clinical Practice Guideline Summary of Surgical Management of Osteoarthritis of the Knee.. The Journal of the American Academy of Orthopaedic Surgeons, 2023. DOI: 10.5435/JAAOS-D-23-00338.