Cartilage is built by specialized cells called chondrocytes, which produce a dense matrix of collagen fibers and water-trapping molecules. Your body assembles this tissue most actively during growth and development, but maintaining it throughout adulthood depends on the right nutrients, physical activity, and growth signals. Understanding what goes into cartilage, and what keeps it healthy, can help you make better choices for your joints.
What Cartilage Is Made Of
Healthy articular cartilage, the smooth layer covering the ends of bones in your joints, is surprisingly simple in composition. Water makes up 65% to 80% of its total weight. Of the remaining dry weight, about 60% is collagen (primarily type II), the protein that gives cartilage its structural framework. The second largest component is a group of molecules called proteoglycans, which account for 10% to 15% of wet weight and are responsible for cartilage’s ability to absorb shock.
The proteoglycan that matters most is aggrecan. Multiple aggrecan molecules attach to a long backbone of hyaluronic acid, forming enormous brush-like aggregates that sit within the collagen network. These aggregates carry a strong negative electrical charge, which pulls water into the tissue and creates osmotic swelling pressure. That pressure is what allows cartilage to compress under your body weight during walking or running and then spring back when the load is removed. Without adequate aggrecan, cartilage loses its cushioning ability.
How Your Body Builds New Cartilage
Cartilage formation, called chondrogenesis, begins when clusters of stem cells condense together and transform into chondrocytes. During this process, the cells shift from producing everyday structural proteins to manufacturing cartilage-specific collagens (types II, IX, and XI). These chondrocytes then secrete the collagen fibers and proteoglycans that form the surrounding matrix.
In adults, this process slows dramatically. The type II collagen network in mature cartilage has an estimated half-life of 117 years, meaning it barely turns over at all unless it’s damaged. Chondrocytes do continue producing proteoglycans and other non-collagen molecules at a low, steady rate, but they can’t easily rebuild the collagen scaffold once it breaks down. This is a key reason cartilage damage is so difficult to reverse.
Why Cartilage Heals So Poorly
Unlike most tissues in your body, cartilage has no blood supply, no nerve fibers, and no lymphatic drainage. It’s only 2 to 3 millimeters thick, and the chondrocytes inside it rely entirely on nutrients diffusing in from the joint fluid. Without blood vessels, your body can’t deliver the inflammatory cells and repair signals that heal a cut or mend a broken bone. A cartilage defect essentially stays a defect unless something intervenes.
Growth Signals That Drive Cartilage Production
Several naturally occurring growth factors regulate how chondrocytes behave. Insulin-like growth factor 1 (IGF-1) stimulates chondrocytes to produce both proteoglycans and collagen, and it also slows the rate at which proteoglycans are lost from the matrix. In lab studies, IGF-1 consistently drives expansive tissue growth and net deposition of proteoglycan in both immature and adult cartilage.
Transforming growth factor beta (TGF-beta) plays a different role. Rather than pushing aggressive new growth, it helps maintain cartilage homeostasis, keeping the tissue’s size, composition, and mechanical function stable. Other growth factors like BMP-7 also promote proteoglycan deposition. Your body produces these signals naturally, and their levels are influenced by factors like physical activity, sleep, and overall metabolic health.
Nutrients Your Body Needs to Make Cartilage
Building the type II collagen that forms cartilage’s structural backbone requires specific raw materials. The main amino acids are proline, glycine, and hydroxyproline, which your body assembles into the characteristic triple-helix shape of collagen fibers. You get these amino acids from protein-rich foods: meat, poultry, fish, eggs, dairy, and bone broth are particularly good sources.
But amino acids alone aren’t enough. Your body also needs vitamin C, zinc, copper, and manganese to complete the collagen assembly process. Vitamin C is especially critical because it’s required to form hydroxyproline, without which collagen fibers can’t hold their shape. A diet that includes citrus fruits, bell peppers, leafy greens, nuts, seeds, and shellfish covers these micronutrient needs for most people.
How Movement Affects Cartilage Health
Physical loading is one of the most powerful signals for cartilage maintenance. Because cartilage has no blood supply, the compression and release cycle during movement is what pumps nutrients in and waste products out. But the type and intensity of loading matters enormously.
Research on chondrocyte responses to mechanical strain has identified a clear dose-response pattern. Very light loading (below about 3% tissue strain) produces little to no biological response from chondrocytes. Moderate loading, in the range of 3% to 10% strain applied rhythmically, triggers anabolic responses, meaning chondrocytes ramp up production of matrix components. But loading above 10% strain, especially if sustained for long periods, flips the switch toward breakdown, with chondrocytes producing more destructive enzymes than building materials.
In practical terms, this means regular moderate exercise like walking, cycling, swimming, and controlled strength training supports cartilage health, while repeated high-impact overloading or prolonged extreme exertion can accelerate damage. Consistency matters more than intensity.
Do Glucosamine and Chondroitin Supplements Work?
Glucosamine and chondroitin are among the most popular joint supplements, marketed as cartilage-building compounds. The logic seems sound: glucosamine is a building block of the proteoglycans in cartilage, and chondroitin is a component of aggrecan. But the clinical evidence for structural benefits is weak.
A randomized, placebo-controlled trial gave 201 people with chronic knee pain either 1,500 mg of glucosamine or a placebo daily for 24 weeks. Using high-resolution 3T MRI to measure cartilage damage across thousands of joint subregions, the researchers found no statistically significant difference in cartilage worsening between the two groups. Only about 1.4% of all scored subregions showed any deterioration over the study period, and the rate was virtually identical whether participants took glucosamine or not. The study’s conclusion was direct: there was no evidence of structural benefit from glucosamine supplementation.
Some people do report feeling less joint pain on these supplements, which may reflect modest anti-inflammatory effects or placebo response. But if your goal is literally building or preserving cartilage tissue, current MRI evidence doesn’t support that these supplements accomplish it.
Medical Procedures That Rebuild Cartilage
When cartilage damage is significant, several surgical approaches can attempt to restore it. The most established is autologous chondrocyte implantation (ACI), where a small sample of your own cartilage cells is harvested, grown in a lab to multiply, and then implanted back into the defect.
Long-term data on ACI are encouraging for the right candidates. Across studies with an average follow-up of over 11 years, 82% of patients had successful outcomes. For smaller defects (under about 4.5 square centimeters), success rates climbed to 92%, with failure rates dropping to under 9%. Larger defects fared significantly worse: the failure rate jumped to nearly 24% for lesions above that size threshold, and over half of those patients needed additional surgery. Younger patients and those with smaller defects consistently did better.
Other approaches include microfracture, which drills tiny holes into bone beneath a cartilage defect to release stem cells that form a repair tissue, and newer techniques using scaffold materials seeded with cells or growth factors. These procedures work best for focal defects in otherwise healthy joints rather than widespread cartilage loss from advanced osteoarthritis.
What Matters Most for Your Cartilage
The factors that matter most for cartilage health are largely within your control. A protein-rich diet with adequate vitamin C and trace minerals provides the raw materials. Regular, moderate-intensity exercise delivers the mechanical stimulation chondrocytes need to stay active and pumps nutrients through the tissue. Maintaining a healthy body weight reduces the chronic overloading that accelerates cartilage breakdown. And protecting joints from acute injuries, especially ligament tears that destabilize the joint, prevents the kind of abnormal loading patterns that chondrocytes can’t compensate for.
What your body can’t do well is rebuild cartilage once the collagen scaffold is significantly damaged. The slow turnover rate of type II collagen means prevention is far more effective than repair. By the time cartilage loss shows up on an X-ray or causes daily pain, the window for simple interventions has often narrowed considerably.