MACI advice

This is part of an ongoing series of posts on what I have learned from an ongoing, chronic knee problem. This post describes how I injured my knee and has links to the posts I have written about other lessons I have learned.

I thought I’d dedicate a post to my advice for people considering MACI based on what I have learned from my journey with MACI, and with knee pain in general.

Ultimately, if you are considering MACI, you have some amount of reduced function due to pain, and you are hoping MACI resolves the root cause of your pain so that you can return to activities you are currently unable to perform.

I’ll summarize my story below so you know where I am coming from, and then I’ll provide my general advice. This advice should be helpful for those who are considering MACI as well as those who had unsuccessful MACI outcomes.

I welcome feedback regarding any inaccuracies or nuances I missed.

My story, briefly

The short version of my story is that I have had patellofemoral and fat pad pain since an ACLR surgery in 2019. The patellofemoral pain has held back my progress more than the fat pad pain. My surgery timeline: ACLR with BTB patella graft Mar 2019, cyclops lesion removal Dec 2019, medial patellar MACI Sep 2023. I have spoken to dozens of knee surgeons and PTs over the past 6 years to try to resolve pain and progress rehab to return to even a fraction of my original activities (running, hiking, etc).

I knew nothing about knees, much less knee pain, prior to the ACLR surgery. Since that surgery, not including work, knee pain and physical therapy consume more of my time than anything else in my life.

I chose MACI after a few surgeons recommended it as a course of action to resolve my knee pain. I had a large and growing cartilage defect (~3cm) on my medial patellar ridge. This made sense to me at the time. Sadly, it did not resolve my pain, and it left me with even stronger patellofemoral pain that I am still treating to this day.

By the end of 2024, it was clear my MACI had failed to resolve my symptoms, which led me to go on my largest quest yet to speak to doctors and knee pain specialists to see what I had missed back when I considered MACI, and what I should do going forward.

Advice to prospective MACI patients

My advice covers the following topics:

1. Understand the possible sources of pain in the knee
2. Find a thoughtful diagnostician (and maybe become one yourself)
3. Ensure cartilage damage is the true root cause of your pain
4. Fully exhaust conservative treatment, even if you think you’ve already tried everything
5. Be wary of Vericel, the studies they provide, and their MACI Mentor program
6. How many and what kinds of doctors to talk to
7. Know what you are getting into

The sources of pain in the knee

Listing all of the possible sources of pain in the knee would require many posts, and I am not a knee doctor. E3 Rehab has a great guide to the types of knee pain. Instead, I’ll walk you through the types of knee pain I experience - fat pad pain and patellofemoral pain - and what I have learned about the possible causes of my pain.

Fat pad pain occurs for me between 30 and 0 degrees of knee flexion (i.e. the end range of extension). At it’s strongest, it’s a painful pinching sensation, and even walking, particularly on flat surfaces, becomes difficult. Terminal knee extension exercises and cycling seem to aggravate my fat pad. There are different presentations of fat pad pain - this is just what I experience. I do not have impingement or lots of fat pad swelling.

Patellofemoral pain for me is strongest between 60 and 90 degrees of knee flexion. I feel the pain over an area (i.e. not sharp) behind my patella. When severe, as it often is, it stops me from progressing physical therapy and doing activities that put significant load on the knee, like hiking downhill.

It is not uncommon for fat pad pain and patellofemoral pain to occur together.

When dealing with patellofemoral pain, it is important to understand the compressive forces at play through your knee joint:

• Walking = ~1/2 of your body weight
• Ascending stairs = ~3x your body weight
• Descending stairs: ~5x your body weight

Find a thoughtful diagnostician

A retired surgeon (who is very familiar with MACI) I saw earlier this year put it well: “find a surgeon who is a thoughtful diagnostician”. The same thing applies to your physical therapist.

A thoughtful diagnostician will do things like:

• Spend sufficient time watching you perform the exact movements that are painful
• Test theories with you, e.g. by having you try certain movements or certain PT techniques and tools
• Potentially offer diagnostic tools like ultrasound-guided lidocaine injections to test theories about the cause of your knee pain

Unless your case is very straightforward, if your surgeon or PT does not spend much time on diagnosis before recommending a surgery or rehab technique, find better care. Many knee pain experts offer virtual appointments if you don’t live close to good medical institutions.

Is cartilage damage the root cause of your pain?

This is the key thing to figure out before operating. There are tons of very active, pain-free people walking around with asymptomatic cartilage defects.

I have learned several things about my knee (sadly, all after my MACI surgery) that made it very unlikely that the MACI surgery I underwent would resolve my knee pain.

1. Medial patellar cartilage damage (i.e. my type of cartilage damage) does not present as pain in the knee as often as lateral patellar cartilage damage. Claire Robertson, a patellofemoral pain expert in the UK, told me about some recent research into which types of cartilage damage present with pain.
2. I had an MRI performed on my non-surgery knee and found that I have similar, though not quite as advanced, cartilage wear in the same exact area. So I am genetically predisposed to medial patellar cartilage wear. I have no pain in this knee.

Ultimately, there are many types of cartilage damage that do not result in a clear-cut diagnosis, so it is likely you will not know with 100% certainty if MACI will solve your issues. But, you can increase your chances of success by spending as much time as possible validating your diagnosis.

Earlier, I described the compressive forces through the knee joint with different activities. You can use this information to help with your diagnosis:

• Where precisely is your cartilage defect?
• In what part of flexion do forces transmit through your cartilage defect? If the defect does not line up with where you experience pain, it’s possible your pain has nothing to do with your cartilage defect.
• Do you know how the defect started to begin with? Have you fully rehabbed your knee from prior injuries/interventions? Faulty knee biomechanics can be at play.

Before embarking on any knee surgery, your surgeon and PT should be able to describe how the cartilage damage you have relates to the knee pain you experience. If that causal relationship is not made clear to you, I would recommend spending more time diagnosing the pain.

One more thing to keep in mind: if you have a cartilage defect, do you understand how it developed? Was there an injury that directly resulted in the damage, or has it worn down over time? If it has worn down over time, is MACI alone enough, or might you need an additional surgery? For example, some people have patellar instability or maltracking resulting in patellar cartilage damage, and they can have a tibial tubercle osteotomy performed in addition to MACI so that they don’t just re-wear the same area of cartilage down.

Fully exhaust conservative treatments

At many points in time over the past 6 years, I have thought I have exhausted conservative treatments like physical therapy and injections, only to be humbled by something I didn’t know.

I will mention various things I have learned to help you consider if you have exhausted physical therapy or not.

• Do you fully understand which activities and movements produce pain? Understanding this will help reduce your pain levels, which will in turn help you progress your rehab.
• Do you have a clear understanding of safe pain vs unsafe pain when exercising? For example, when treating patellofemoral pain, it is common to experience pain during exercise. If you avoid all pain, you’ll never get stronger. If you push too hard through pain, you’ll trigger trigger inflammatory responses that will end up setting you pain. Generally, 1/10 - 3/10 pain during exercise is safe if you are not stiff or in pain after exercising.
• Be wary of post-exercise stiffness. Some activities do not hurt much during, but if they cause stiffness that lasts for hours or days afterward, it is causing inflammation and should be scaled back.
• If you are trying to build strength but are blocked by pain, have you tried blood flow restriction (BFR)? EMS/TENS? Compression sleeves? Medializing patellar braces? Tape techniques with KT tape or leukotape? All of these have helped me in the past.
• Are you resting enough? Some people push too hard too soon.
• Are you resting too much? If you scale back activity too much, you will atrophy, which can lead to more pain.
• Have you worked with a great PT before? A great PT will help you think through everything I mentioned above. A bad PT will give you a canned set of exercises and send you on your way.

Injections are also an option, and there are more options and nuance here than I thought!

• Most people know about cortisone shots. What I didn’t know is that there are more injection options, some of which can be guided by ultrasound, and the delivery location matters. Cortisone shots can be used to reduced inflammation in a muscle or in the fat pad, for example, without as much risk to cartilage damage as if you administer them intra-articularly.
• Numbing substances like lidocaine can be administered by ultrasound to help diagnose where pain originates in your knee. I had ultrasound-guided lidocaine injected as a diagnostic tool to help distinguish between fat pad and patellofemoral pain in my knee (i.e. is the pain coming more from inside or outside the knee joint).
• Toradol is an anti-inflammatory alternative to cortisone that can be injected to reduce pain.
• I’ve been aware of injections like PRP and hyaluronic acid for a while, but the results seem mixed based on the studies I’ve seen. Maybe I’ll try one someday.
• The thinking with injections in general is that they can buy you a window to strengthen your knee if you have yet to recover symmetrical strength after a trauma or surgery. In my case, I have persistent quad weakness, as it common post-ACL, post-MACI, and after long duration patellofemoral pain.

I personally did not benefit from other treatments like acupuncture and sports massage.

Vericel is not your friend (or your enemy)

Vericel is the corporation that develops, produces, and sells MACI in the United States.

Be wary of Vericel, the studies they provide, and their MACI Mentor program. They are trying to “close” you as patient. They make money on each MACI surgery performed. They will provide you with biased studies whose authors have conflicts of interest. MACI mentors are a biased sample of patients with successful outcomes who are paid for the phone calls they take.

Vericel wants your money, or rather, your insurance provider’s money.

I do not think MACI is a sham surgery or anything like that, but I do think any advice or marketing you receive from Vericel should be fully discounted when you are considering MACI.

Vericel will help you in getting insurance approval, which is nice.

(Side note: “MACI Arthro” is a thing now, meaning MACI can be applied arthroscopically, which is less invasive than open knee surgery. Pretty cool!)

How many and what kinds of doctors to talk to

I strongly recommend getting multiple opinions prior to committing to a MACI surgery.

Seek out the very best doctors at the best medical institutions you can access. You’re looking for someone with lots of experience who has seen a lot of knees. The simplest way to ensure that is to look for a doctor that has been practicing for 10+ years, e.g. the head of sports medicine or orthopedic surgery. Ensure the doctor is up-to-date on recent techniques.

MACI itself is not actually that complex of a surgery, but the diagnosis leading to MACI is complex.

Definitely talk to a surgeon who specializes in cartilage repair. You want somebody who has performed MACI before and can help you decide between MACI and other cartilage repair options.

I also recommend talking to at least one surgeon who knows MACI and other cartilage techniques, but is not necessary specialized in cartilage repair. I have found cartilage-focused doctors to often be so focused on the cartilage damage itself that they look past other potential causes of pain. Your experience may differ from mine on this - my point here is to talk to a doctor or surgeon who has the knowledge and experience to look at your knee holistically.

I also recommend talking to orthopedic doctors and physical therapists who do not perform surgery. Generally, surgeons are more likely to recommend surgery than non-surgeons. A good doctor or PT can provide you with some other ideas.

If this is your first time with knee-related medical expenses, this can sound time-consuming and potentially expensive, but the downside cost of making the wrong decision here is immense, both in terms of time and your long-term outcome. Take the time and expense to get multiple opinions. Whatever time and money you spend here will likely be dwarfed by the expense of the surgery itself and, in particular, the post-surgery physical therapy and tools you will purchase.

You will hear different perspectives. In the end, you are gathering information to make a decision regarding whether to proceed with MACI. Only you can make this decision, and only you will live with your knee long-term.

Know what you are getting into

Remember: MACI is a big surgery with a long recovery time. Many patients have long periods of reduced weight-bearing. The atrophy can be significant, and new damage can occur during rehab. Given the difficulties of diagnosing pain caused by cartilage defects, ensure MACI is the right choice for you.

I know knee pain is frustrating. Many of us were very active prior to our knee pain, and we are willing to do almost anything to get back to that level of function. MACI is often presented as a good solution when a patient has pain and there are cartilage defect(s) in their MRIs. Sadly, it is not this simple. Take the time to validate your diagnosis before embarking on MACI.

In case it’s not clear, I am not against MACI! It’s a great tool for some types of cartilage repair, and a nice alternative to even more invasive techniques like OATS. I know people who have had successful MACI outcomes, as well as people who haven’t. What I have learned is that knee pain is complex and cartilage damage is not always the root cause.

I hope this advice is helpful. I’m very grateful to have this community. I have even had the pleasure of talking to some of you over the phone! Good luck to everyone here as we all work to resolve our knee pain.