Cartilage is a firm, flexible connective tissue that cushions your joints, holds open your airways, shapes your nose and ears, and serves as the template for bone growth during childhood. It shows up in more places than most people realize, and each location demands a slightly different version of the tissue. Three distinct types of cartilage handle these jobs across the body.
The Three Types of Cartilage
Your body produces three varieties of cartilage, each built for a specific kind of work. Hyaline cartilage is the most common. It lines the ends of bones inside joints, reinforces the trachea, shapes the nose, and connects the ribs to the breastbone. It’s smooth, glassy, and exceptionally good at reducing friction. Elastic cartilage is more flexible. It gives structure to your outer ear, the epiglottis (the flap that covers your windpipe when you swallow), and parts of the larynx. It can bend and spring back without breaking. Fibrocartilage is the toughest of the three. You’ll find it in the knee’s meniscus, between the vertebrae of your spine, and where tendons and ligaments attach to bone. It’s built to absorb heavy, repeated loads.
Cushioning and Protecting Your Joints
The cartilage coating the ends of your bones inside a joint, called articular cartilage, does two things at once: it creates an almost frictionless surface for movement and it distributes the mechanical forces that come with every step, squat, or twist. The surface layer is coated with a protein called lubricin and reinforced by horizontally aligned collagen fibers, which together make the joint glide smoothly. Deeper inside the tissue, a dense network of proteins absorbs and spreads out the force of impact so no single point on the bone takes the full load.
In a healthy adult knee, this cartilage layer is only about 2 to 2.5 millimeters thick on average, roughly the width of two stacked credit cards. Despite being thin, it handles enormous forces. The thickest cartilage in the knee sits on the back of the thighbone (around 2.5 mm), while the thinnest areas sit closer to 2 mm. That slim layer is all that stands between bone surfaces during every movement you make.
Absorbing Shock in the Spine and Knees
Fibrocartilage acts as the body’s shock absorber in high-stress locations. The meniscus in your knee is a good example. Its wedge shape and layered collagen fibers convert downward force into outward “hoop” stresses, spreading the load across a wider area instead of concentrating it on one spot. The deeper layers contain collagen fibers running in circles around the meniscus, while the surface fibers run radially. This arrangement lets the tissue handle compression, shear, and tension simultaneously.
Water plays a surprisingly large role here. A mature meniscus is about 72% water by weight. That water binds to molecules called proteoglycans inside the tissue, creating hydraulic pressure that resists compression. When you land from a jump or push off while running, the fluid pressure inside the meniscus helps absorb the impact before it reaches the bone.
The intervertebral discs in your spine work on a similar principle. These fibrocartilage pads sit between each vertebra, cushioning the spine during walking, bending, and lifting. Without them, the vertebrae would grind directly against each other.
Keeping Your Airways Open
Cartilage rings in the trachea and larynx prevent your airway from collapsing every time you inhale. The trachea is reinforced by C-shaped rings of hyaline cartilage that hold it open like the wire coils inside a vacuum hose. In the larynx, the cricoid cartilage forms the only complete ring and is critical for maintaining airway stability. It also serves as an anchor point for the muscles and ligaments that open and close the vocal cords during speech.
How essential is this structural support? When surgeons have had to remove the cricoid cartilage entirely, patients often cannot breathe independently afterward. In one surgical series, only one out of three patients could have their breathing tube removed after total cricoid removal, because the soft tissue left behind couldn’t keep the airway open on its own.
Building the Skeleton During Childhood
Before your bones were bones, most of them were cartilage. During fetal development and childhood, cartilage acts as a scaffold that gradually transforms into bone through a process called endochondral ossification. The growth plate, a band of cartilage near each end of a long bone, is where this happens.
Inside the growth plate, cartilage cells divide and stack into columns, secreting a surrounding matrix that eventually mineralizes. As these cells mature, they coordinate their own death and release signals that attract blood vessels and bone-building cells. New bone tissue replaces the cartilage from the inside out, lengthening the bone in the process. This cycle repeats throughout childhood and adolescence. When all the cartilage cells in the growth plate finally die off and are replaced by bone, the plate closes and leaves behind a faint line called the epiphyseal scar. That closure marks the end of height growth.
Why Cartilage Heals So Slowly
One of cartilage’s defining traits is also its biggest vulnerability: it has no blood supply. Unlike muscle or skin, cartilage is avascular. Its cells, called chondrocytes, make up only about 2% to 5% of the total tissue and depend entirely on nutrients diffusing in from the surrounding joint fluid and underlying bone. Small molecules pass through relatively easily, but larger or electrically charged molecules have a harder time penetrating the dense, negatively charged matrix.
This limited nutrient access is a major reason cartilage repairs itself so poorly. When damage occurs, chondrocytes try to produce new matrix material, but much of it leaks into the joint space instead of filling the defect. At the same time, harmful substances that are normally kept out of cartilage, like certain immune proteins, can reach the cells through the damaged area and trigger further breakdown. In mature joints, a layer of calcified cartilage at the bone-cartilage boundary adds another barrier that restricts nutrient flow to the tissue above it.
This is why cartilage injuries, whether from a sports accident or years of wear, tend to be long-lasting problems. The tissue simply doesn’t have the biological infrastructure to rebuild itself the way vascularized tissues do.
Shaping the Nose and Ears
Elastic cartilage gives your outer ear its shape and flexibility. You can fold your ear flat and it springs right back, something bone could never do. The same type of cartilage shapes the epiglottis, which needs to flex rapidly every time you swallow to seal off the airway. Hyaline cartilage handles the nose, providing the firm but slightly bendable bridge and tip structure. These areas don’t bear heavy loads, but they need a material that holds a defined shape without being rigid or brittle.