MACI Myths: Debunking Three Knee Cartilage Repair Misconceptions Skip to content

MACI Myths: Debunking Three Knee Cartilage Repair Misconceptions

Surgeons wrap a knee following knee cartilage repair surgery.

When researching treatment options like MACI knee cartilage repair, it’s easy to stumble upon misconceptions.

Let’s get down to the facts. Below we debunk some common myths about the procedure.


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MACI Myths – Debunked

Myth: MACI cell therapy is an experimental treatment.

Fact: MACI is an FDA-approved treatment that uses your own cells to repair your knee cartilage damage. Results with MACI have been reported in over 49 publications and five randomized clinical trials.

During the SUMMIT clinical trial, researchers compared the results of microfracture, a long-standing procedure that also treats knee cartilage damage, to MACI surgery. In the trial, a significantly greater proportion of patients treated with MACI showed clinically meaningful improvements in both pain and function at two years after their procedure, when compared to microfracture.1 In a follow-up study, those improvements were maintained at five years after the procedure.2

Only a trained specialist can perform the MACI procedure. Before choosing what, if any, surgical procedure is best, you and your surgeon will consider your overall health and age, whether you have more than one cartilage injury, the size of your injury, and the type and length of rehabilitation that is appropriate for you.


Myth: Most patients will be immobile during their recovery from MACI.

Fact: Post-surgery, most patients are, in fact, weight-bearing and ambulatory with crutches relatively quickly.

After MACI surgery, you will begin a physician-prescribed rehabilitation program specifically designed for you. While each patient’s rehab experience is unique and individual results will vary, a typical patient will experience progressive gains throughout the 6- to 9-month rehab process.

Common post-surgery rehab milestones include:

  • Within the first week post-op: Patients are mobile with crutches.
  • 0-3 months post-op: Return to light recreational movement including the ability to walk, use a stationary bike, get back to daily routines (showering, navigating stairs, driving, etc.) with the assistance of crutches and resume work if the role can be performed seated.
  • 3-6 months post-op: Return to low-impact activities (golfing, yoga, rowing, swimming, etc.) and resume more physically demanding jobs and activities that require strength and endurance.
  • 6-9+ months post-op: Return to pre-injury level of sports, work and recreational activities.


Myth: You should wait to get treatment for your knee cartilage damage.

Fact: Knee cartilage doesn’t heal on its own and often gets worse over time. And in fact, delaying treatment can make repairs more difficult down the road.

A study called “Time Matters” explores how delaying treatment for knee cartilage pain can lead to worsening injury. Data showed that patients undergoing cell-based knee cartilage repair (like MACI) who experienced a long delay between biopsy and implantation were at greater risk for cartilage defect expansion and the appearance of new defects. Timely treatment with MACI knee cartilage repair can help heal knee cartilage damage and prevent further deterioration. It is important to spot the symptoms of knee cartilage damage early, and talk to your doctor about your treatment options, timeline and goals.


Please see below for full indication and ISI. Blog posts are intended to provide educational information only and do not constitute medical advice. Always talk to your doctor with any questions.


1. In a responder analysis, at 104 weeks following treatment the proportion of subjects with at least a 10-point improvement in both KOOS pain and function (SRA) was greater in the MACI group (63/72=87.5%; 95% CI [77.6%, 94.1%]) compared with the microfracture group (49/72=68.1%; 95% CI [56.0%, 78.6%]).[Saris D, Price A, Widuchowski W, et al. for the SUMMIT study group. Matrix-applied characterized autologous cultured chondrocytes versus microfracture: two-year follow-up of a prospective randomized trial. Am J Sports Med. 2014;42:1384-1394.]

2. All subjects from the 2-year study had the option to enroll in a 3-year follow-up study (extension study), in which 128 subjects participated. All 65 subjects (100%, 65/65) in the MACI group and 59 subjects (93.7%, 59/63) in the microfracture group completed the extension study. The mean 2-year KOOS pain and function scores remained stable for the additional 3-year period in both treatment groups. (Table 1) [Brittberg M, Recker D, Ilgenfritz J, Saris D. SUMMIT Extension Study Group. Matrix-applied characterized autologous cultured chondrocytes versus microfracture: Five-year follow-up of a prospective randomized trial. Am J Sports Med. 2018;46(6):1343-1351.]


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Indication and Important Safety Information

Important Safety Information

MACI should not be used if you:

  • are allergic to antibiotics such as gentamicin, or materials that come from cow, pig, or ox;
  • have severe osteoarthritis of the knee, other severe inflammatory conditions, infections or inflammation in the bone joint and other surrounding tissue, or blood clotting conditions;
  • have had knee surgery in the past 6 months, not including surgery for obtaining a cartilage biopsy or a surgical procedure to prepare your knee for a MACI implant;
  • or cannot follow a doctor-prescribed rehabilitation program after your surgery

Consult your doctor if you have cancer in the area of the cartilage biopsy or implant as the safety of MACI is not known in those cases.

Conditions that existed before your surgery, including meniscus tears, joint or ligament instability, or alignment problems should be evaluated and treated before or at the same time as the MACI implant.

MACI is not recommended if you are pregnant.

MACI has not been studied in patients younger than 18 or over 55 years of age.

Common side effects include joint pain, tendonitis, back pain, joint swelling, and joint effusion.

More serious side effects include joint pain, cartilage or meniscus injury, treatment failure, and osteoarthritis.

Please see Full Prescribing Information for more information.


MACI® is made up of your own (autologous) cells that are expanded and placed onto a film that is implanted into the area of the cartilage damage and absorbed back into your own tissue.

MACI® (autologous cultured chondrocytes on porcine collagen membrane) is made up of your own (autologous) cells that are expanded and placed onto a film that is implanted into the area of the cartilage damage and absorbed back into your own tissue.

MACI is used for the repair of symptomatic cartilage damage of the adult knee.

The amount of MACI applied depends on the size of the cartilage damage. The MACI film is trimmed by your surgeon to match the size and shape of the damage, to ensure the damaged area is completely covered.

Limitations of Use

It is not known whether MACI is effective in joints other than the knee.

It is not known whether MACI is safe or effective in patients over the age of 55 years.