Cartilage injury occurs when the smooth tissue covering the ends of bones in joints becomes damaged, leading to pain, swelling, and difficulty with movement that can affect your ability to enjoy everyday activities.

Cartilage is a tough yet flexible tissue that plays a critical role in keeping our joints working smoothly. When you think about all the movements your body makes throughout the day—walking, climbing stairs, bending down to pick something up, or playing sports—your joints are constantly at work. At the ends of your bones where they meet to form joints, there is a thin layer of tissue called articular cartilage, which simply means cartilage related to joints. This tissue acts like a cushion between bones, allowing them to glide over each other without friction, almost like the smooth surface of a skating rink allows skaters to move freely.^[1]

The smooth covering formed by articular cartilage has been compared to the consistency of linoleum flooring—it’s slippery and durable, designed to handle the heavy loads and constant use that joints experience over a lifetime. Inside your joints, fluid lubricates this cartilage, making movement even smoother. This remarkable tissue doesn’t just reduce friction; it also absorbs shock, protecting your bones from the impacts of daily life. When you jump, run, or even just walk, your cartilage takes on much of the force, preventing your bones from grinding against each other.^[1]

However, despite being strong and resilient, cartilage has a significant weakness. Unlike many other tissues in your body, cartilage does not have its own blood supply. Blood carries oxygen and nutrients that help tissues heal when they’re damaged. Without this blood supply, cartilage has very limited ability to repair itself when it gets injured. This means that once cartilage is damaged, it often doesn’t heal well on its own, and the injury can lead to ongoing problems.^[1][3]

How Common Are Cartilage Injuries?

Cartilage injuries are surprisingly common, particularly among people who are physically active. Studies looking at knee arthroscopy procedures—where doctors use a small camera to look inside the knee joint—have found that approximately sixty percent of patients undergoing these procedures have significant cartilage damage. These injuries often involve damage to fifty percent or more of the cartilage surface, which is considered high-grade damage.^[4]

The knee is by far the most commonly affected joint when it comes to cartilage injuries, though these injuries can also occur in the hip, ankle, shoulder, and elbow. Among Americans, knee problems are particularly widespread. According to the National Institutes of Health, about one-third of adults over the age of forty-five experience some type of knee pain, and cartilage damage is often a contributing factor.^[3]

Articular cartilage injuries affect people across all age groups and activity levels. Young athletes who participate in sports that involve twisting, pivoting, or high-impact movements are at particular risk. However, cartilage damage isn’t limited to athletes. People who have experienced accidents, falls, or other trauma can also suffer cartilage injuries. Additionally, as people age, the natural wear and tear on joints can lead to cartilage deterioration, which is why older adults are also commonly affected.^[4]

What Causes Cartilage to Become Damaged?

Cartilage damage can happen in several different ways. One of the most straightforward causes is a direct, forceful impact to a joint. This might occur during a car accident, a hard fall, or a collision during sports. When a joint receives a powerful blow, the cartilage can tear, crack, or break away from the underlying bone. Athletes who play contact sports or participate in activities that involve sudden stops and direction changes are particularly vulnerable to these types of injuries.^[1]

Another common cause of cartilage damage is twisting the joint while it’s bearing weight. Imagine a soccer player who plants their foot firmly on the ground and then suddenly pivots or changes direction. The twisting force on the knee while it’s supporting the full weight of the body can damage the cartilage. This type of injury is especially common in sports like soccer, basketball, and football.^[1]

Repetitive smaller impacts to a joint can also wear down cartilage over time. People whose jobs or hobbies involve repeated stress on their joints may gradually develop cartilage damage. For instance, workers who spend years kneeling or squatting, or runners who log thousands of miles over many years, may eventually develop cartilage problems from the cumulative effect of all those impacts.^[1]

Progressive wear and tear is another major cause of cartilage damage. As we age, our cartilage naturally experiences decades of use. Every step we take, every time we bend or lift something, our cartilage is working. Over time, this constant use can cause the cartilage to thin out and deteriorate. This type of gradual breakdown is the hallmark of osteoarthritis, a condition where the protective cartilage wears away, leading to pain and stiffness in the affected joint.^[1]

Finally, poor alignment of joints due to birth abnormalities or previous injuries can contribute to cartilage damage. When a joint isn’t properly aligned, the forces acting on it aren’t distributed evenly. This means some areas of cartilage experience more pressure than they should, leading to faster wear and eventual damage.^[1]

Who Is Most at Risk?

Certain groups of people face higher risks of developing cartilage injuries. Athletes and physically active individuals are at the top of the list, especially those involved in high-impact sports or activities that require sudden movements, jumping, or twisting. Sports like soccer, basketball, football, and skiing carry particularly high risks for cartilage damage.^[1]

Young adults who tear their anterior cruciate ligament (ACL)—one of the major ligaments in the knee—or damage their meniscus—a different type of cartilage that cushions the knee—are at especially high risk for articular cartilage injuries. When these supporting structures are damaged, the knee becomes less stable. This instability allows the joint to make abnormal movements, which can quickly wear down or damage the articular cartilage.^[21]

People who are overweight or obese face increased risk as well. Every extra pound of body weight puts additional stress on weight-bearing joints, particularly the knees. This excess load accelerates cartilage wear and increases the likelihood of injury. The relationship between weight and joint health goes beyond just mechanical stress, however. Body fat itself produces chemicals that promote inflammation—swelling and irritation in tissues—which can contribute to cartilage breakdown.^[19]

Individuals with joint instability or poor joint alignment also face elevated risks. If a joint doesn’t move correctly or isn’t properly aligned, certain areas of cartilage experience uneven pressure. Over time, this can lead to accelerated wear in those spots. People who have had previous joint injuries are also at higher risk, as earlier damage can affect how the joint functions going forward.^[1]

Finally, certain occupations and habits increase risk. Jobs that require repeated kneeling, squatting, or heavy lifting put extra strain on joints. Similarly, people who engage in repetitive movements during work or recreational activities may gradually damage their cartilage over time through overuse.^[8]

Recognizing the Symptoms

When cartilage becomes damaged, it typically causes several recognizable symptoms. The most common complaint is joint pain. This pain often gets worse when you use the affected joint and tends to improve when you rest. For example, if you have cartilage damage in your knee, walking, climbing stairs, or playing sports might cause significant discomfort, but sitting down and resting your leg may provide relief.^[1]

Swelling in the affected joint is another frequent symptom. The joint may appear puffy or enlarged compared to the same joint on the other side of your body. This swelling occurs because of inflammation in the joint tissue or because fluid accumulates inside the joint space. Some people describe their swollen joint as feeling warm to the touch or appearing red.^[1][3]

Stiffness is also common with cartilage injuries. You might notice that your joint feels tight or difficult to move, especially first thing in the morning or after sitting still for a long time. The joint may not bend or straighten as easily as it should, and you might find that your range of motion—how far you can move the joint—is limited compared to before the injury.^[1][3]

Many people with cartilage damage report unusual sounds or sensations in their joints. You might hear a clicking, popping, or grinding noise when you move the affected joint. Some describe a feeling that something is catching or getting stuck inside the joint. These sensations occur because the damaged cartilage no longer provides a smooth surface for the bones to glide over.^[1]

In more severe cases, pieces of damaged cartilage can break off and float around inside the joint. These fragments are called loose bodies, and they can cause the joint to lock up or suddenly give way. When this happens, you might find that you can’t fully bend or straighten your joint, or that it suddenly stops moving mid-motion. This can be frightening and may make it impossible to continue your normal activities.^[7]

Preventing Cartilage Injuries

While not all cartilage injuries can be prevented, there are several steps you can take to reduce your risk and protect your joints. One of the most important strategies is maintaining a healthy body weight. Research has shown that for people with osteoarthritis of the knee, losing even a modest amount of weight can help reduce symptoms. In one study, overweight or obese adults who lost twenty percent or more of their body weight reported significantly less pain and were able to walk farther than those who lost less weight. Keeping your weight in a healthy range reduces the stress on your weight-bearing joints and decreases the chemicals that promote inflammation.^[19]

Regular physical activity is also crucial for joint health. Exercise helps in several ways: it strengthens the muscles that support and stabilize your joints, improves balance (which can prevent falls and injuries), and helps maintain a healthy weight. The key is choosing activities that are gentle on your joints. Low-impact exercises like swimming, cycling, walking, and yoga are excellent choices. These activities provide cardiovascular benefits and strengthen muscles without putting excessive stress on joint cartilage.^[19]

If you participate in sports, using proper technique is essential. Many cartilage injuries occur because of incorrect form or technique during athletic activities. Working with a coach or trainer to ensure you’re moving correctly can help prevent injuries. Additionally, wearing appropriate protective equipment and footwear designed for your specific activity can provide extra protection for your joints.^[1]

For athletes and active individuals, avoiding overtraining is important. Giving your body adequate time to rest and recover between intense workouts or competitions allows your joints to recover from the stresses they’ve experienced. Overuse injuries develop gradually when joints don’t get enough recovery time, leading to cartilage damage that accumulates over weeks or months.^[1]

Addressing joint instability or alignment problems early is another prevention strategy. If you’ve had a previous injury to ligaments or other joint structures, following through with recommended rehabilitation and treatment can help prevent secondary cartilage damage. When joints are stable and properly aligned, forces are distributed evenly across the cartilage, reducing the risk of excessive wear in any one area.^[21]

Understanding What Happens in Your Body

To understand what happens when cartilage is damaged, it helps to know a bit about how this remarkable tissue is structured. Articular cartilage consists of specialized cells called chondrocytes embedded in a complex network of proteins and other molecules. The main structural protein is collagen, particularly type 2 collagen, which forms a mesh-like framework. This framework is filled with molecules called proteoglycans and glycosaminoglycans, which attract and hold water. In fact, about ninety percent of cartilage is water. This water content is crucial because it allows the cartilage to compress and rebound, acting as an effective shock absorber.^[14]

Healthy articular cartilage is organized into four distinct layers, each with different characteristics. These layers vary in their cell density, the composition of their protein networks, and how their collagen fibers are arranged. This sophisticated structure allows cartilage to withstand enormous forces—when you walk up or down stairs, your knee cartilage experiences forces equivalent to five to seven times your body weight.^[21]

When cartilage is damaged, this carefully organized structure breaks down. The injury might start with the cartilage surface becoming roughened or developing cracks. As damage progresses, the cartilage may soften and begin to fragment. Pieces can break away, exposing the bone underneath. Once the protective cartilage layer is gone, bone rubs directly against bone during movement, which is extremely painful and causes further damage.^[7]

Because cartilage lacks a blood supply, it cannot mount the typical healing response that other tissues use when they’re injured. When you cut your skin, for example, blood rushes to the area bringing cells and nutrients that start the repair process. Cartilage doesn’t have this capability. The chondrocytes—the cartilage cells—have very limited ability to multiply and produce new tissue, especially in adults. This is why cartilage injuries are so challenging to treat and why they often don’t heal on their own.^[9]

As cartilage damage progresses, it can trigger a cascade of problems in the joint. The damaged cartilage may release fragments into the joint fluid, causing inflammation and irritation. The inflammation can spread to other joint structures, including the synovial membrane that lines the joint and produces lubricating fluid. This widespread inflammation causes pain, swelling, and stiffness. Over time, if the cartilage damage is severe or extensive, it can lead to osteoarthritis, where the entire joint becomes affected.^[4]

Interestingly, when cartilage damage extends deep enough to reach the bone underneath, the bone can contribute to the healing process. The bone has a rich blood supply, and when it’s penetrated, blood cells and stem cells can migrate into the damaged area. These cells can form repair tissue, although this tissue is typically fibrocartilage rather than the original hyaline articular cartilage. Fibrocartilage is tougher but less elastic than hyaline cartilage, and it doesn’t have the same smooth surface or wear characteristics. While it’s better than having no cartilage at all, it may not hold up as well over the long term.^[4]