What to ask about microfracture surgery and Matrix-based autologous chondrocyte implantation (MACI)

Questions to bring about the damaged spot

Ask where the damage sits and how large it is. The surgeon also checks the bone and whether your knee sits straight and stays steady. Wear across the knee can make a small repair less useful. Your age and earlier knee operations matter too.

Before agreeing, ask whether the rest of your knee can support the repaired area as you return to walking, climbing stairs and doing the daily tasks you miss without more soreness. Ask what the surgeon expects you to feel during that return. A scan may show repair tissue filling the area while soreness stays the same.

What to plan for after the operation

Recovery isn't quick just because the repaired area is small. You'll need to protect the knee while repair tissue forms. Physical therapy brings back motion and strength over time. Ask when you can drive, work and use stairs.

MACI includes an earlier procedure to collect your cartilage cells. It'll add time and cost before the repair operation. Microfracture takes one operation, though recovery still requires work. Ask for each schedule on paper.

What to do when surgery may not fit

A surgeon may say broad wear makes either repair a poor fit. That answer doesn't leave you without help. Ask about exercise, physical therapy and ways to ease the load. Less soreness and better motion are worthwhile aims.

If you've tried that care and still hurt, seek another careful review. Bring your scan and notes from earlier visits. Ask what non-surgical care may do for soreness and motion. You can take time before paying for a long recovery.

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.