Knee cartilage has very limited ability to repair itself, which makes “rebuilding” it one of the harder problems in orthopedics. Cartilage has no blood supply, so it can’t rely on the normal healing process your body uses for cuts, broken bones, or muscle tears. That said, there are surgical procedures that can regrow cartilage in specific situations, lifestyle changes that protect what you have left, and several options in between. What works for you depends on how much cartilage you’ve lost, where the damage is, and your age.
Why Cartilage Doesn’t Heal on Its Own
Cartilage is maintained by cells called chondrocytes, which sit embedded in a dense matrix of collagen and water. In adults, these cells have very low activity. They barely divide, and the collagen fibers they produce are meant to last a lifetime with minimal replacement. This is the opposite of tissues like skin or bone, where cells are constantly turning over.
The root of the problem is that cartilage has no blood vessels. Most tissues heal by flooding the injured area with blood, delivering stem cells and growth factors to rebuild damaged structures. Cartilage gets its nutrients only through slow diffusion from the joint fluid and underlying bone. This means that once cartilage is damaged, whether from injury or gradual wear, your body simply can’t mount a meaningful repair response. A small surface scratch might go unnoticed for years. A deeper defect will generally stay the same size or get worse.
Surgical Options That Regrow Cartilage
For focal cartilage defects (a specific area of damage rather than widespread arthritis), several surgical procedures can stimulate new cartilage growth or transplant healthy cartilage into the damaged zone.
Microfracture
This is the simplest approach. A surgeon pokes small holes through the bone beneath the damaged cartilage, allowing blood and stem cells to seep into the defect and form a repair layer. The catch is that the tissue it produces is fibrocartilage, a tougher, less elastic material than the original hyaline cartilage your knee was born with. Fibrocartilage doesn’t handle joint forces as well over time, so while microfracture can reduce pain and improve function, the repair tissue may break down again, especially in active people or larger defects.
MACI (Autologous Chondrocyte Implantation)
MACI is a two-stage procedure and currently one of the most advanced options for regrowing true cartilage. In the first stage, a surgeon takes a small sample of your healthy cartilage cells during an arthroscopy. Those cells are grown in a lab over about four weeks and seeded onto a collagen membrane. In the second surgery, the surgeon prepares the damaged area, removes any hardened bone, and fixes the cell-seeded membrane into the defect with dissolvable stitches or biological glue.
In a long-term study following patients for up to 10 years, 68% achieved complete filling of their cartilage defect on MRI. Imaging scores remained stable between the one-year and eight-year marks, suggesting the repair tissue holds up well over time. MACI works best for younger, active patients with a well-defined area of damage rather than widespread cartilage loss.
Osteochondral Autograft Transfer (OAT)
This procedure transplants a plug of healthy cartilage and bone from a non-weight-bearing area of your knee into the damaged zone. The advantage over microfracture is that it restores actual hyaline cartilage to the joint surface instead of fibrocartilage. It works well for smaller defects but is limited by how much donor cartilage your knee can spare.
Recovery After Surgery
Initial healing from cartilage restoration surgery takes roughly six weeks. Returning to full activities like jogging or running typically takes three to six months. The new cartilage tissue continues to mature and strengthen well beyond that window, so patience with rehabilitation matters.
PRP and Stem Cell Injections
Platelet-rich plasma (PRP) and stem cell injections are widely marketed for cartilage regeneration, but the clinical evidence doesn’t support the claims most clinics make.
The largest and most rigorous PRP trial, published in JAMA, compared PRP injections to placebo (saline) injections in 288 patients with knee osteoarthritis over 12 months. Pain improved in both groups by nearly the same amount: 2.1 points in the PRP group versus 1.8 points in the placebo group, a difference that was not statistically significant. More importantly, MRI measurements showed that cartilage volume continued to decline in both groups at essentially the same rate. PRP did not slow cartilage loss or rebuild any tissue.
Stem cell therapy for knee cartilage is still largely experimental. Most published human studies are small, early-phase safety trials rather than rigorous comparisons against a placebo or standard treatment. Some studies involved injecting cell suspensions directly into the knee but showed no evidence the cells were actually responsible for tissue repair. The FDA classifies these cell products as “more than minimally manipulated,” meaning clinics offering them outside of approved clinical trials may be operating in a regulatory gray area. If a clinic guarantees cartilage regrowth from stem cell injections, that claim isn’t supported by the current evidence.
Exercise That Protects and Stimulates Cartilage
While exercise can’t regrow lost cartilage, mechanical loading during joint movement is essential for maintaining what you have. Cartilage relies on compression and release to draw in nutrients from the surrounding joint fluid, almost like squeezing and releasing a sponge. Without regular movement, chondrocytes become less active and the tissue deteriorates faster.
The most beneficial pattern for cartilage health mirrors natural movement: alternating between moderate activity and periods of rest, with occasional higher-intensity efforts. In practical terms, this means a mix of walking, cycling, or swimming combined with strengthening exercises for the muscles around the knee, especially the quadriceps. Stronger muscles absorb more shock before it reaches the joint surface. Research on cartilage cells shows that this kind of cyclical, moderate loading reduces the oxidative stress that drives cartilage breakdown, suggesting that consistent exercise therapy may slow the progression of osteoarthritis.
High-impact activities aren’t necessarily off limits if your cartilage damage is mild, but repeatedly loading a joint that’s already significantly damaged can accelerate wear. Low-impact options like cycling and pool-based exercise deliver the mechanical stimulus cartilage needs with less compressive force.
Weight Loss Has a Measurable Effect
Carrying extra weight accelerates cartilage loss, and reducing it has a direct, measurable protective effect. A 48-month MRI study from the Osteoarthritis Initiative found that for every 1% of body weight lost, there was a statistically significant reduction in cartilage deterioration scores across the knee. The effect was most pronounced in the inner (medial) side of the knee, which bears the most load during walking.
This doesn’t mean weight loss rebuilds cartilage. It means it slows the rate of further loss, which for many people is the most impactful single change they can make. Combined with exercise, weight loss is considered the first-line approach for managing early to moderate knee osteoarthritis, and it’s effective enough that many patients delay or avoid surgery.
Supplements: What the Evidence Shows
Glucosamine and chondroitin are the most studied supplements for knee cartilage. The landmark GAIT trial, published in the New England Journal of Medicine, enrolled 1,583 patients and tested glucosamine (1,500 mg daily), chondroitin sulfate (1,200 mg daily), or both together over 24 weeks. For the overall group, none of the supplement regimens performed significantly better than placebo for pain relief. A subgroup of patients with moderate to severe pain did show some benefit from the combination, but this was a secondary finding and not the study’s primary result.
Undenatured type II collagen (UC-II) is a newer supplement that works through a different mechanism, essentially training the immune system to be less aggressive toward cartilage proteins. Studies have used a dose of 40 mg daily for 90 days and reported improvements in pain and function scores. The evidence base is smaller than for glucosamine, but the early results are more consistently positive.
Vitamin C plays a known role in collagen synthesis, which is the structural backbone of cartilage. Severe deficiency impairs the body’s ability to maintain cartilage tissue. Most people get enough vitamin C from their diet, but ensuring adequate intake through fruits and vegetables supports the basic biochemistry your chondrocytes need to function.
Matching the Right Approach to Your Situation
The right strategy depends entirely on the type and extent of your cartilage damage. For a focal defect from an injury in an otherwise healthy knee, surgical options like MACI or osteochondral grafting offer the best chance of actual cartilage regrowth. For widespread cartilage thinning from osteoarthritis, surgery is less likely to help, and the focus shifts to slowing further loss through weight management, consistent low-impact exercise, and possibly supplements.
If your cartilage loss is mild and you’re mostly dealing with stiffness or occasional pain, the combination of strengthening exercises, maintaining a healthy weight, and staying active may be enough to keep your knees functional for years. If you have a defined cartilage defect that’s causing mechanical symptoms like catching or locking, imaging and a conversation with an orthopedic surgeon can clarify whether a restorative procedure makes sense for your specific anatomy.