Humans have salamander-like ability to regrow cartilage in joints

Orthopedic surgeon here. Articular cartilage regeneration is definitely the holy grail of my field, but for all of the promises of biologics (growth factors, stem cells, collagen matrices) it always seems to be “another five years away”.

The part of this article that I find most interesting was identifying a marker that can differentiate ankle cartilage vs the hip. This is certainly a phenomenon that we all observe clinically, hip and knee arthritis is vastly more common than ankle arthritis despite the weight bearing surface of the ankle being significantly smaller (meaning more force per square area). When we do encounter ankle arthritis, it is almost always the result of prior intra-articular fractures or instability from chronic ligamenous injuries, not the normal osteoarthritic age related degeneration we see in hips and knees.

Let’s find out what makes ankle articular cartilage so special and sprinkle it in our hips and knees.

I wish this was true. I've had cartilage damage in my elbow from sports and have gone through major surgery over it. This technology has always been '10 years away'; from mesh or paste with stem cells, to other 'new' technology to regrow it. It simply is not there yet. I check every year, I reach out to any doctor starting a clinical trial. Hyaline cartilage does not regenerate naturally. The best they can do is get the body to reproduce Fibro cartilage which is essentially scar tissue. For those wondering about what treatments are available, check out Microfracture (breaks bone to release bone marrow cells to generate Fibro), OATs (osteochondral autograft transfer system) which pulls cartilage out of other areas and then places them in the damaged area. If this were to ever be true, it would be the biggest breakthrough in quality of life improvements for seniors as they are the most likely to experience breakdown in cartilage in joints. It severely limits their mobility.

I had a pretty horrific left knee injury wrestling. I was carted off to the hospital, when the accident was described to the Orthopedic surgeon he actually recoiled and was concerned I may have totally destroyed my and that it might not be repairable, it was 1979. From the time of the accident until I was in surgery it was less than 3 hours.

Somehow I managed to only stretch all my knee ligaments, ACL PCL,MCL,LCL, a few small inline tears, but nothing severed, but he said they were like overused rubber bands all stretched out. I did however shred all the cartilage. The cartilage was a mess, so much so that when they surgically removed all the cartilage from my knee. I have the video of the surgery, all my knee cartilage was removed, they scraped the bones in order to give me the smoothest ride possible, but it doesn't do much. When you don't have cartilage in your knee it's pretty obvious.

Fast forward 22 years to mid 2001 when I start following the teachings of Linus Pauling regarding L-Ascorbic Acid and L-Lysine for heart disease prevention. I started taking high levels of both in divided doses during the day. My stress levels plummeted, and my overall health significantly improved, but after about 6 months I started to notice my knee was changing, a lot. My pain was going away and I didn't notice the bone on bone activity, after about 9 months my knee stopped hurting completely.

In fact it felt so good that I started walking for exercise, normally after 5 minutes of walking I felt like I was gun shot in the knee, but nope I was able to walk fine for as long as I wanted. I then started jogging and then running, no pain, no pain at all.

I've seen my orthopedist and while he's not willing to just give me and MRI, based on all of his examination he said my left knee is no different then my right knee and he didn't believe me that I had all my cartridge surgically removed 20 years before. I took the video, just in case, and I played the video. My knee has a unique scar from when I was a child and fell on a bottle, I had the scar when they performed the surgery and shot the video and I still have the scar, so there is no doubt that all my cartridge in my knee was surgically removed in 1979.

L-ascorbic acid and L-Lysine are basic building blocks for cartilage. I'm just a sample size of one, but I know my cartilage is back, maybe not all the way back, but more than enough back that my knee rock solid stable, it's smooth as silk, I have no pain and my orthopedist can't find a difference in my knees.

For what it's worth.

This is something I have long suspected. I have definitely heard of instances where friends subsequent MRIs have shown regrown cartilage in the knee, but years later. And it doesn't happen for everyone. The friends that regrew, they were runners, they took their injury seriously, they kept moving but were very serious about maintaining flexibility, diet, hydration, etc. I think if you wear down your cartilage, but do nothing to address the tightness that caused the wear in the first place, then you will not see regrowth. The fact that this is an interesting research finding is reflective of somewhat a sad fact in my eyes: people generally do not take care of themselves, instead hoping for surgery or a pill or procedure. Few will add an hour of rehabilitative work to their daily routine and instead just live with the issue forever and complain. I have herniated discs, torn bicep tendons, had tendonitis nearly everywhere at one point or another, sublexed my knees, but nearing 40 I still am active as ever with no daily pain. Some of these injuries took me years to recover from, but recover I did.

There is nothing proven in this article. They seem to have some new insights into the process, but they have not demonstrated any capability yet.

We all have the ability to generate cartilage and limbs, that's how we got those things. The open question remains as to why some animals can do so again and humans dont.

Children under the age of seven or so can regrow the severed tip of a finger.

See https://en.wikipedia.org/wiki/The_Body_Electric_(book) and "What Bodies Think About: Bioelectric Computation Outside the Nervous System (youtube.com)" https://news.ycombinator.com/item?id=18736698

As someone in my late 20s with cartilage damage in both my knees and back due to sports, this progress can’t come soon enough. I miss running a lot (and miss not having constant back pain), and it’s confounding to me why something that appears so simple, cartilage repair, has made almost no real progress over decades (I know it’s not simple). I keep following the research and hoping new discoveries will eventually lead to something tangible.

Link to the actual paper: https://advances.sciencemag.org/content/5/10/eaax3203

On a somewhat-related note: would glucosamine chondroiton pill speed this process? There's a lot of debate whether they do anything at all.

I have broken my both knee cartilages. First time when I was 23 and recently when I was 35. Fist knee recovered successfully after some years (I'd say about 5 years). The second injury was 2 years ago and the knee is almost 100% recovered, I feel some little pain only after running 10K and also after playing soccer.

Both injuries were in the outer meniscus. There is a difference in the inner and the outer meniscus (perhaps the inner cannot recover because of less blood flow?). I didn't go to surgery.

Things I can do without any pain whatsoever: running 5K at a fast pace, karate, barbell squat.

I had to have surgery for a minor tear in my wrist a few years ago. They didn't know going in precisely what they'd find, but knew that if it was a portion that had blood flow, they could repair and thing would grow back. If there was no blood flow, they most they could do was clean the tear area, stitch things back a bit, but they'd always be a little weak and I'd always have to be careful not to reinjure.

One interesting tidbit that this article doesn’t mention is that fiber orientation of cartilage is fundamental to the functionality of different cartilaginous tissues. It’s similar to how fiber orientation in carbon fiber parts will be adjusted to provide strength and durability in specific directions. Articular cartilages likely is somewhat more evenly oriented, but tendons are highly aligned to length and meniscus aligned in a hoop like direction. New or repaired cartilage in different tissues need exercise and other forms of mechanical agitation to align properly. Even if we could repair all cartilage readily we’d still need lots of physical therapy and to regrow damaged tissue at a slow pace. So no miracle sir on the couch cures even if this works.

On another the meniscus (and vertebrae discs?) loose blood flow after mid-30 or thereabouts and might make effective delivery or healing more difficult. It’ll be interesting to see what happens in the next decade or two!

My son lost a chunk of his thumb joint to a router accident. The doctor saw the mess, and bandaged it up for 6 days to let the bleeding/soft tissue damage resolve some.

When unbandaged 6 days later, the thumb cartilage in that joint was back, and the thumb worked fine. No surgery; no more attention needed. Still working 10 years later!

I've suspected that cartilage regenerates ever since I learned that long term knuckle cracking doesn't cause long term damage, despite the audible crack coming from cavitation (which can be very destructive to things like ship propellers, eroding the metal over time.)

If it didn't, my hands would probably be crippled by now.

I recently read _The Body Electric_ and it gives insights into the body regenerating limbs.

Has anyone any experience with stem cells? I believe the efficacy of PRP pales by comparison although I'm pleased to hear others success with it.

I have stage 3 chondromalacia + flat feet + loose joint, an incredibly unholy trinity. Nothing amount of PT seems to work and the arthsocopy didn't help much either. If anyone's got any tips, I'd love to hear them.

So, this would seem to open up possibilities for transplants and/or gene therapy?