Knee cartilage damage can be managed and sometimes repaired, but it cannot fully heal on its own. Cartilage lacks blood vessels, nerves, and lymphatic tissue, which means your body has no built-in way to deliver the repair cells and nutrients it sends to heal other injuries like muscle tears or broken bones. The chondrocytes (the only cells living inside cartilage) divide slowly and produce very little new tissue. So “fixing” cartilage damage really means choosing from a range of treatments that reduce pain, slow progression, or surgically restore the joint surface, depending on how severe your damage is.
Why Cartilage Doesn’t Heal Like Other Tissue
When you cut your skin or strain a muscle, blood rushes to the area carrying oxygen, growth factors, and immune cells that kick off healing. Cartilage gets none of that. It has no blood supply at all. Its cells rely on a slow, inefficient energy process and reproduce at a fraction of the rate of most other cells in your body. This is why a cartilage lesion that might seem minor can persist for years and gradually worsen with continued use.
How Cartilage Damage Is Graded
Doctors classify cartilage damage on a scale from Grade 0 (healthy, intact cartilage) to Grade 4 (cartilage completely worn away, with bare bone exposed underneath). Grading is done through MRI or by direct visualization during arthroscopy. The grade matters because it determines which treatments are realistic. A shallow surface softening (Grade 1 or 2) responds well to conservative approaches, while a deep defect exposing bone (Grade 4) typically requires surgical intervention.
Non-Surgical Options
Physical Therapy and Exercise
Structured rehab is the first line of defense for most cartilage injuries. The goal is to strengthen the muscles around your knee so they absorb more impact and reduce the load on damaged cartilage. Early exercises focus on gentle, cyclic motion: heel slides, stationary cycling with minimal resistance, or pool-based therapy. Loading is increased gradually, and your therapist monitors for signs that the joint is being overworked. For damage on the kneecap surface, weight-bearing exercises (like standing and walking) can progress faster, but bending the knee under load is introduced more slowly. The reverse is true for damage on the main weight-bearing surfaces of the knee.
Injections: PRP vs. Hyaluronic Acid
Two of the most common injection therapies are platelet-rich plasma (PRP), made from your own blood, and hyaluronic acid (HA), a lubricant that mimics your joint’s natural fluid. A large systematic review comparing the two found that PRP outperformed hyaluronic acid on both pain and function scores at every follow-up point through 12 months. In the first three months, PRP and HA reduced pain by similar amounts. But by six months and one year, PRP pulled clearly ahead.
Neither injection is a permanent fix. Hyaluronic acid tends to wear off within one to six months, with patients often returning to their pre-treatment pain levels. PRP results are more variable: some studies show benefits lasting about two months, while others report improvement persisting up to a year and a half. Both options are best thought of as pain management tools that buy time and improve quality of life rather than as cures.
Weight Loss
If you’re carrying extra weight, losing it is one of the most effective things you can do for a damaged knee. Research on joint loading found that for every kilogram of body weight lost, the peak force on your knee drops by 2.2 kilograms at a given walking speed. That’s roughly a 1-to-2 ratio: lose 10 pounds and you take about 20 pounds of pressure off your knee with every step. Over thousands of steps per day, this adds up to a massive reduction in wear on the remaining cartilage.
Supplements
Glucosamine and chondroitin are among the most popular joint supplements, but the clinical evidence is underwhelming. A network meta-analysis found no significant difference between glucosamine and placebo for knee pain scores. Undenatured type II collagen ranked lowest among all tested supplements for pain relief and was also not significantly better than placebo. These products are unlikely to cause harm, but you shouldn’t count on them to meaningfully repair or protect cartilage.
Surgical Repair: Microfracture
Microfracture is one of the most common cartilage procedures. A surgeon pokes small holes into the bone beneath the damaged area, allowing blood and marrow cells to seep up and form a clot that eventually becomes new tissue. The catch is that this new tissue is usually fibrocartilage, a tougher, less smooth material than the original hyaline cartilage that lines healthy joints. Think of it as a patch rather than a true restoration.
Long-term data reflect this limitation. In one comparative study, the survival rate of microfracture repairs dropped below 80% within the first year and below 60% within three years. The overall long-term failure rate was 66%, with the average time to failure being just four years. Microfracture works best for small lesions in younger, active patients who need a bridge solution, but it is not a durable long-term repair for most people.
Surgical Repair: Cartilage Transfer (OATS)
Osteochondral autograft transfer, commonly called OATS or mosaicplasty, takes small plugs of healthy cartilage and bone from a non-weight-bearing area of your knee and transplants them into the damaged spot. Because it moves real hyaline cartilage rather than generating a fibrocartilage substitute, it tends to last longer than microfracture. In the same long-term study, the OATS survival rate stayed above 80% for seven years and above 60% for 15 years. The average time to failure was 8.4 years, more than double that of microfracture.
The trade-off is that OATS is best suited for defects of about 3 square centimeters or smaller, with an upper limit of 4 to 6 square centimeters. Larger areas of damage don’t leave enough healthy donor tissue to work with and require a different approach.
Surgical Repair: Cell-Based Regeneration (MACI)
For larger defects, a procedure called MACI (matrix-induced autologous chondrocyte implantation) offers a more advanced option. It’s a two-stage process: first, a small sample of your cartilage cells is harvested and grown in a lab over several weeks. Then, the expanded cells are seeded onto a scaffold and implanted into the defect during a second surgery.
Recovery from MACI is significant. You’ll wear a locked knee brace day and night for six weeks and use crutches, bearing no weight on the surgical leg for the first 10 to 14 days. During those initial six weeks, you’ll also use a continuous passive motion machine for about two hours daily to keep the joint mobile while the new tissue integrates. The bending goal is 60 degrees by your first follow-up (around two weeks) and 90 degrees by the six-week mark. Formal physical therapy starts within the first week and continues two times per week for three to six months. If it’s your right knee, expect not to drive for roughly six weeks after the brace comes off. Full return to high-impact activity can take nine months to over a year.
Stem Cell Therapy: Where Things Stand
Stem cell injections generate enormous interest, but they remain largely experimental for cartilage repair. These therapies use cells (often harvested from bone marrow or fat) that have the potential to develop into cartilage tissue. Early clinical evidence suggests they may reduce pain and improve function, and newer approaches combining stem cells with 3D-printed scaffolds or engineered growth signals show promise in animal models.
The practical reality is that most of these strategies are still in preclinical or early-phase human trials with small patient groups and short follow-up periods. Challenges around whether the transplanted cells actually survive in the joint, potential immune reactions, and long-term safety have not been fully resolved. No stem cell product is currently FDA-approved specifically for cartilage regeneration, and treatments marketed at clinics vary widely in quality and evidence behind them.
Choosing the Right Approach
The best treatment depends on the size and depth of your cartilage defect, your age, your activity level, and how much the damage affects your daily life. Small, shallow lesions often respond well to physical therapy, weight management, and periodic PRP injections. Focal defects under 3 square centimeters in active patients are strong candidates for OATS. Larger defects or those that have failed a prior microfracture may benefit from MACI. For widespread, end-stage cartilage loss (Grade 4 across a large area), partial or total knee replacement becomes the most reliable option for restoring function.
No single treatment works for everyone, and many people end up using a combination: rehab to stabilize the joint, injections for flare-ups, and surgery if and when conservative measures stop providing enough relief. Getting an accurate diagnosis with MRI and a clear understanding of your defect’s grade and size is the essential first step in making a decision you’ll be satisfied with long-term.