Costal cartilage connects the ribs to the sternum (breastbone). These bars of flexible cartilage extend from the front ends of the ribs toward the center of the chest, creating a semi-rigid bridge that holds the rib cage together while still allowing it to expand when you breathe.
What Costal Cartilage Is
Costal cartilage is made of hyaline cartilage, the same smooth, glassy type found on the surfaces of most joints. Each rib has its own strip of costal cartilage at its front end. The cartilage is firm enough to hold the rib cage’s shape but flexible enough to bend slightly with every breath. This elasticity is what allows your chest wall to move rather than being a locked, rigid box.
Where the rib meets its cartilage, the two tissues blend together seamlessly. The outer covering of the cartilage is continuous with the outer covering of the bone itself, so the connection is extremely strong. This junction is called the costochondral joint.
How the Three Rib Types Attach Differently
Not all 12 pairs of ribs connect to the sternum in the same way. They fall into three groups based on how (or whether) they reach it.
- True ribs (ribs 1 through 7) have their own individual strip of costal cartilage that attaches directly to the sternum. These are the most secure connections, and they provide the main structural stability of the front of the rib cage.
- False ribs (ribs 8 through 10) don’t reach the sternum on their own. Instead, their costal cartilages curve upward and fuse into the cartilage of the rib above, ultimately linking to the seventh rib’s cartilage. This creates the costal arch, the curved ridge you can feel along the bottom edge of your rib cage.
- Floating ribs (ribs 11 and 12) have no connection to the sternum at all. Their short cartilage tips end freely in the muscles of the abdominal wall.
The Joints That Hold It All Together
Two separate joints exist along each rib’s path to the sternum, and they work differently from each other.
The costochondral joint is where bone meets cartilage at the front end of the rib. This is a fixed connection with no joint capsule or fluid. The tissues are essentially fused, which is why rib fractures at this spot are uncommon.
The sternocostal joint is where the cartilage meets the sternum. The first rib’s connection here is also a fixed, fused joint. But ribs 2 through 7 form true synovial joints at the sternum, meaning they have a small capsule filled with lubricating fluid and can glide slightly. This subtle movement is part of what makes breathing possible. A set of fan-shaped ligaments called the radiate sternocostal ligaments reinforces each of these joints on the front of the chest.
For the false ribs, the cartilages of ribs 8 through 10 connect to each other through small gliding joints called interchondral joints, which allow a bit of sliding motion between them.
Why This Flexibility Matters for Breathing
Every time you inhale, your rib cage expands in three directions: front to back, side to side, and top to bottom. The upper true ribs swing upward and forward in what anatomists call a “pump handle” motion, pushing the sternum outward and increasing the front-to-back depth of your chest. Without the built-in give of costal cartilage and its synovial joints at the sternum, this motion would be impossible.
The flexibility of costal cartilage also absorbs impacts. A direct blow to the chest compresses the cartilage slightly before force transfers to bone, which helps protect the heart and lungs behind it.
How Costal Cartilage Changes With Age
Costal cartilage is meant to stay flexible for life, but it gradually calcifies and stiffens as you get older. This process is considered normal physiology rather than disease. Calcification typically begins to appear in your mid-20s, starting at the rib end and slowly progressing toward the sternum over decades.
Men tend to show calcification earlier and more intensely than women, with noticeable differences appearing as early as age 16. The gap narrows by the mid-60s, when both sexes approach similar levels of stiffness. Before age 40, calcification patterns tend to be simple and linear. After 40, the patterns become more complex and irregular. This gradual stiffening is one reason older adults often notice their chest feels less flexible, and it can contribute to slightly shallower breathing over time.
The process is so predictable that forensic scientists use the degree of costal cartilage calcification on CT scans to help estimate a person’s age.
Costochondritis: When the Connection Gets Inflamed
The most common problem affecting the rib-to-sternum connection is costochondritis, an inflammation of the costal cartilage where it meets the sternum. It causes a sharp or dull pain in the upper front of the chest that gets worse with movement, deep breaths, coughing, or stretching. The hallmark sign is that pressing on the spot where a rib meets the breastbone reproduces the pain, usually at just one or two specific points.
Costochondritis is benign, but it frequently mimics more alarming conditions like heart problems, which is why many people end up in an emergency room before getting the diagnosis. There’s typically no swelling, fever, or shortness of breath. A related but less common condition called Tietze syndrome involves visible swelling at the joint, usually around the second or third rib.