Ask Dr. Skendzel: How Does Articular Cartilage Support Knee Function?
Our knees glide obediently every time we take a step, sit, or crouch, thanks to the cartilage that coats bone ends and cushions weight-bearing bones. We asked Dr. Skendzel to explain the types of cartilage found in our knee joint.
Understanding knee cartilage types
“Knee injuries are an area of focus for me, so I get questions about cartilage all the time,” says sports medicine surgeon Dr. Jack Skendzel. “The knee is the largest joint in the body, and relies on two knee cartilage types to function effectively: fibrocartilage and articular cartilage. When you understand knee cartilage types and how to care for them, you can help prevent injury and unnecessary wear and tear.
Comparing Fibrocartilage and articular cartilage
“The crescent-shaped pad of cartilage called the meniscus is made of tough fibrocartilage. It functions as a joint stabilizer and a cushion between the weight-bearing bone surfaces in the knee. A second type of cartilage in the knee joint is the smooth shiny white articular cartilage. Articular cartilage coats the ends of the bones in the knee joint to provide a smooth gliding surface so the bones in the joint move fluidly against each other.” These two knee cartilage types are important for optimal joint function.
Damage can be done to both the meniscus fibrocartilage and the slick articular cartilage through traumatic injury, degenerative tears over time, or a genetic profile that predisposes cartilage to early deterioration. Generally, problems with articular cartilage are caused by bad genetics or by trauma like ACL injury or kneecap dislocation.
When describing damage to articular cartilage specifically, Dr. Skendzel distinguishes between localized injuries and overall cartilage degeneration. “Active men and women can develop a focal or localized defect in the articular cartilage coating,” he says. “This can occur behind the kneecap, in the groove that the kneecap sits in, or on the inside or outside of the knee. You are missing cartilage in a specific area, but the surrounding cartilage is healthy and intact. It’s like a pothole in a road. We have a number of treatment options for these focal defects that are most appropriate for patients under 40 years of age.
“However,” he continues, “we take a very different approach when the problem involves an overall degradation of the joint cartilage, called diffuse arthritis. As we age, our joint cartilage may slowly wear away, making joint movement painful. Unfortunately, we have very few options to offer patients when that happens, other than knee replacement.”
One of the factors making cartilage repair challenging is that it is difficult to regrow. There are no blood vessels in cartilage to supply nutrients our tissues need to recover. Instead, cartilage tissue receives nutrients from the synovial fluid, and those nutrients are delivered by joint movement. If joints become painful to move, nutrient supply to the cartilage is affected.
“It is also important to understand that you can never replace the articular cartilage you were born with,” explains Dr. Skendzel. “Even when treatments do stimulate cartilage to grow back, the new growth is fibrocartilage, not articular cartilage. The fibrocartilage that your body is able to grow will never have the same gliding properties as the original articular cartilage, but a repair can return patients to a more active lifestyle than they’d otherwise have. The bottom line? It’s important to protect your cartilage. The younger you are, the better your body will probably respond to regrowing cartilage. If you think you may have a cartilage injury, don’t delay diagnosis and treatment.”
Additional resources for you:
- Check out the article: Understand Your Joints: What Is Cartilage?
- More from Dr. Skendzel on cartilage: What Can I Expect After Knee Cartilage Surgery?
- Get the answer: How is Cartilage Repaired?
- More on Summit’s Sports Medicine services
- From American Academy of Orthopedic Surgeons (trusted external resource): Cartilage Restoration
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