Why Cartilage Damage Doesn't Heal on Its Own
Updated: 4 days ago
Most tissue in your body repairs itself. A broken bone knits back together, a torn muscle rebuilds, a cut in your skin closes within a few days.
Cartilage does none of that. Damage to the cartilage in your knee stays damaged, which surprises most patients the first time they hear it.
It can also get taken the wrong way. "It can't heal" sounds like a countdown, and people walk out of appointments thinking their knee is on a clock. The way I put it is that you can still drive on an old road. The surface isn't what it was and it's never going to resurface itself, but that's a separate question from whether it needs work right now.
What is cartilage?
Articular cartilage is the smooth white covering on the ends of the bones where they meet inside a joint. In the knee it lines the end of the femur, the top of the tibia, and the back of the kneecap. It's two to four millimeters thick.
Think of it as the finish on a hardwood floor. It's thin, it takes all of the contact, and it's there so the structure underneath does not become damaged. Cartilage is slick enough that your femur glides across your tibia thousands of times a day without wearing out.
The same tissue does the same job in the shoulder and the hip.
Not all cartilage is the same
When discussing cartilage, it's important to note that there are different types of cartilage material in the body. Two of them come up constantly in the orthopedic specialty specifically.
Hyaline cartilage is the articular cartilage, the glassy low-friction surface capping the ends of the bones inside of a joint. It's built to glide. It also has no blood supply anywhere in it.
Fibrocartilage is tougher and more fibrous, built to absorb compression instead of glide. It's the shock absorber. Your meniscus is fibrocartilage, so is the labrum in your shoulder and hip, and so are the discs in your spine. Parts of it do have a blood supply, which is why a tear in the outer meniscus can often be repaired while a tear in the inner portion usually gets trimmed out instead.
There's a third kind, elastic cartilage, that makes up your ear and epiglottis. It never comes up in joint problems.
Why it can't repair itself
Everything traces back to the absence of a blood supply. When you fracture a bone, blood floods the area carrying oxygen, nutrients, and the cells that rebuild tissue. Blood vessels are the delivery route for every repair your body performs, and nothing runs into hyaline cartilage. There's no road in, so the crew never arrives.
Two other things compound it. The cells that maintain cartilage, called chondrocytes, are sparse, and they sit locked inside the matrix they built. They can't crawl toward an injury the way cells elsewhere do. Cartilage also has no nerve endings, so it can't produce pain by itself. When a knee with cartilage damage hurts, that pain is coming from the joint lining, the bone underneath, or the capsule. Damage can move along quietly for years before a person feels anything.
Scar tissue
There's one exception to all of this, and it explains a lot of confusing outcomes.
A defect in hyaline cartilage does sometimes fill in. It can happen on its own when the injury goes deep enough to reach the bone, and a surgeon can cause it deliberately in a procedure called microfracture. But what grows in isn't hyaline cartilage, because your body can't make more of that. It fills the hole with fibrocartilage, the same fibrous material your meniscus is made of, showing up here as scar tissue in a place it was never meant to be.
Fibrocartilage beats an open defect. It covers exposed bone and it can settle symptoms down. It's also a different material with different properties: rougher, so it doesn't glide like a smooth hyaline surface; less organized inside, so it spreads load less evenly onto the bone underneath; and less durable under repetitive force, so it can wear through again in a way the original surface wouldn't have.
That accounts for a pattern I see fairly often. A patient is told the defect filled in, and they still hurt, or they feel great for a couple of years and then slide backward. The hole got covered, but the joint surface they had before is gone.
What happens over time
Potholes start as a break in the surface, and the edge is where everything unravels. Traffic catches the lip, the borders crumble, and the bare patch keeps spreading out from what used to be a single crack.
Cartilage defects behave the same way. That edge takes shear force with every step. That defect widens, load that used to spread across a broad surface starts concentrating into a smaller area, and the bone underneath absorbs more of it. Bone responds to the extra load by getting denser and forming spurs along the edges. When that shows up on imaging, we call it arthritis. In a lot of knees it's the downstream result of cartilage damage that couldn't be repaired, rather than a separate disease that arrived later.
How fast that progression moves varies a great deal from one knee to the next. Size and location of the defect, how your leg is aligned, your weight, what you do all day, and whether your meniscus is intact all feed into it.
You can still drive on an old road
A road with cracks in it is still a road. Some get patched in one spot, some get repaved eventually, and plenty just keep carrying traffic for another twenty years with nobody giving them a thought.
Knees are similar. Cartilage wear is close to universal with age, and if I imaged a hundred people in their sixties who walked in with no complaints, a lot of those scans would show it. That's what a knee that's been used looks like.
What actually brings someone in is symptoms. Pain that won't quit. A knee that catches or gives out. Swelling that keeps coming back after a hike, or the slow realization that you've stopped doing something you used to do without ever deciding to.
The exception is a knee with one defined defect and healthy cartilage around it. That's a situation where surface procedures are on the table, and they come off the table once wear spreads across the joint. So timing matters there. That doesn't mean you should go looking for problems in a knee that isn't giving you any.
How it gets diagnosed
Symptoms alone won't tell us it's a cartilage damage issue. Several different knee problems produce identical complaints and get treated in completely different ways.
History and physical exam
How it started, what makes it worse, whether the knee catches or gives way, where the pain actually sits. The exam covers range of motion, stability, alignment, and which structures reproduce your pain when I stress them.
X-ray
X-rays don't show cartilage at all. They show bone, and they show the gap between bones. That gap narrows as cartilage thins, so an X-ray tells us indirectly how much you have left. We take them standing because the joint space looks different under your body weight than it does lying on a table. X-rays also pick up spurs and alignment problems.
MRI
This is what shows the cartilage itself, along with the meniscus, ligaments, and the bone underneath. An MRI is how we find a focal defect, measure it, locate it, and separate a cartilage problem from a meniscus tear or ligament injury.
Arthroscopy
Sometimes we assess the joint surface directly with a camera during surgery. It's the most accurate look at cartilage available, and it isn't a first step.
Treatment options
We're not trying to regrow cartilage. We're changing the things that determine how much the damage affects you day to day: load through the joint, the strength supporting it, how you move, and inflammation inside the joint.
Non-surgical
Physical therapy
Strengthening your quadriceps, hamstrings, and hip muscles changes how force distributes across the knee. We have physical therapy on site in both Austin and Georgetown, which keeps it coordinated with everything else in your care.
Activity and load modification
Changing which activities you do and how much, without giving up activity.
Weight management
Your knee absorbs several times your body weight with every step, so the math works in your favor here. Losing a pound takes roughly four pounds of load off the joint. Ten pounds down is closer to forty pounds off the knee, every step you take.
Bracing
An unloader brace shifts force off the affected side of the joint in certain wear patterns.
Anti-inflammatory medication
These medications will treat the symptoms and provide temporary relief.
Corticosteroid injection
An anti-inflammatory placed directly in the joint for pain and swelling.
Hyaluronic acid injection
A viscous fluid injected into the joint, used in some cases of knee arthritis.
PRP and regenerative injections
Platelet-rich plasma is prepared from your own blood and injected into the joint.
Surgical
Meniscus repair or partial meniscectomy
These options depend on where the tear is. The outer meniscus has a blood supply and can be repaired. The inner portion doesn't, so we trim the torn segment instead, which would be a partial meniscectomy.
Joint replacement
When wear is advanced and nothing else controls symptoms, we replace the worn surfaces. Depending on the pattern, that can mean part of the knee or all of it.
Cartilage restoration
These target the joint surface itself instead of the mechanical symptoms around it, and they're on the table when the damage is focal, with healthy cartilage still surrounding it, rather than wear spread across the joint.
Several procedures exist. Microfracture prompts the body to patch the defect with fibrocartilage, while osetochondral autograft transfer, osteochondral allograft transplantation, and MACI put hyaline cartilage back onto the surface. Which one fits a given knee depends on the size and depth of the defect measured off of the MRI, where it sits in the joint, whether the bone underneath is involved, and how your leg is aligned. A misaligned knee loads a repaired surface unevenly, so alignment sometimes has to be corrected at the same time.
I've covered each of those procedures, the measurements that decide between them, and what's still in development in a separate post on cartilage restoration options.
When to come in
Make an appointment if you've
had knee pain past six weeks
catching or locking, a knee that gives way
swelling that keeps returning after activity
or pain that's changed what you do
If none of that describes your knee, age by itself isn't a reason to have it looked at.
What to take from this
Cartilage doesn't heal, and no amount of rest or time changes that. It still isn't the emergency it often gets treated as.
Wear is normal. A knee with an imperfect surface can carry you a long way, the same as an old road carries traffic. You can't undo the damage. What you can change is how hard that knee has to work, and that's most of what treatment actually is: building up the muscles around it, taking load off of it, adjusting how you move, and addressing weight when that's part of the picture.
Symptoms are what change the conversation. A knee that starts catching, swelling, giving out, or hurting in a way that sticks around is telling you something, and finding out whether it's damage to one spot or general wear is what determines the options you have.
Common questions about cartilage damage
Can cartilage grow back?
Not on its own. Cartilage has no blood supply, so the healing response that repairs bone and muscle never reaches it. Any tissue that fills a defect is fibrocartilage, which isn't the same material as the original joint surface.
Is the meniscus the same as cartilage?
The meniscus is cartilage, but a different type. It's fibrocartilage, a tougher shock-absorbing tissue that sits between the joint surfaces. The cartilage covering the ends of the bones is hyaline cartilage. They're built differently and they heal differently.
Does an X-ray show cartilage damage?
No. X-rays show bone. What they show is the space between bones, which narrows as cartilage thins, so an X-ray indicates cartilage loss indirectly. An MRI is what shows the cartilage itself.
Does cartilage damage always turn into arthritis?
Not always, and not at a predictable rate. Size and location of the defect, leg alignment, body weight, activity demands, and whether the meniscus is intact all affect how a joint changes over time.
Can cartilage damage be painful if cartilage has no nerves?
Yes. The pain comes from the surrounding structures rather than the cartilage itself: the joint lining, the bone underneath, and the joint capsule. That's why damage can progress for a long time before symptoms appear.
Dr. Robin sees patients in Austin and Georgetown for knee, shoulder, and hip problems. Call 512-856-1000 to schedule an evaluation or request an appointment here.
