The sternum is the flat, narrow bone running vertically down the center of your chest. Sometimes called the breastbone, it connects to your ribs and collarbones to form the front wall of your rib cage. It protects your heart, lungs, and major blood vessels from impact, and it serves as an anchor point for muscles and ligaments that move your arms and help you breathe.
The Three Parts of the Sternum
The sternum isn’t one seamless bone. It’s made up of three distinct segments stacked top to bottom: the manubrium, the body, and the xiphoid process.
The manubrium is the top section, roughly rectangular in shape. If you press your fingers into the soft dip at the base of your throat, you’re touching the top edge of the manubrium, a landmark called the suprasternal notch (or jugular notch). The manubrium connects to your collarbones on either side and to your first pair of ribs.
The body is the longest part of the sternum. It’s a flat plate with shallow ridges along its edges where the cartilage of ribs 3 through 7 attaches. Where the manubrium meets the body, there’s a slight forward angle you can often feel through the skin. This ridge is called the sternal angle (also known as the angle of Louis), and it’s one of the most useful landmarks in medicine because the second pair of ribs attaches right at that point. Doctors and paramedics use it to quickly count ribs and locate structures inside the chest.
The xiphoid process is the small, triangular piece at the very bottom of the sternum. In younger people it’s mostly cartilage, gradually hardening into bone over decades. You can sometimes feel it as a small pointed bump just below where your ribs come together.
How Ribs Connect to the Sternum
Your first seven pairs of ribs, called “true ribs,” attach directly to the sternum through strips of flexible cartilage. This cartilage gives the rib cage some elasticity, which matters every time you breathe. When you inhale, your ribs need to swing slightly outward and upward to expand the chest cavity. Without that cartilage buffer, the rigid bone-to-bone connection would make deep breathing much harder.
Ribs 8 through 10 connect indirectly, linking to the cartilage of the rib above rather than to the sternum itself. Ribs 11 and 12, the “floating ribs,” don’t connect to the sternum at all.
What the Sternum Does
The most obvious job of the sternum is protection. It sits directly in front of the heart, which lies just behind and slightly to the left of the breastbone. The major blood vessels entering and leaving the heart, along with the upper portions of both lungs, are all shielded by this bony plate.
The sternum also serves as a structural anchor. The large chest muscles that move your arms originate in part from the sternum. Muscles involved in breathing, including the diaphragm (which attaches near the xiphoid process), also connect here. Without the sternum tying the rib cage together at the front, these muscles would have no stable surface to pull against.
Like other flat bones, the sternum contains bone marrow that produces blood cells. This is why bone marrow biopsies are sometimes performed on the sternum, though this carries a small risk. About 9% of people have a natural hole (called a sternal foramen) somewhere in the bone, and in a small percentage of those cases, the protective tissue around the heart sits directly behind that opening. At least 14 cases of cardiac puncture from sternal needle procedures have been documented, 8 of them fatal. This is rare, but it’s one reason many doctors prefer the hip bone for marrow biopsies.
How the Sternum Develops and Changes
The sternum starts as multiple separate pieces of cartilage in the developing fetus. These gradually harden into bone and fuse together over the course of your life. The segments of the body fuse during childhood and adolescence, but the lowest segment, the xiphoid process, takes much longer. Fusion of the xiphoid to the body of the sternum typically begins in the third decade of life and is complete in most people by their mid-40s. The average age of full fusion is around 46 in men and 45 in women. After age 37 or so, the vast majority of people have a fully fused xiphoid. This predictable timeline is actually useful in forensic medicine, where the degree of sternal fusion can help estimate a person’s age.
Common Causes of Sternum Pain
Pain in or around the sternum is common and usually not dangerous, but it can be alarming because it’s easy to confuse with heart-related chest pain. The most frequent cause is costochondritis, an inflammation of the cartilage connecting the ribs to the sternum. It produces sharp, localized tenderness that gets worse when you press on the area or take a deep breath. It typically resolves on its own over days to weeks.
Other chest wall causes include joint inflammation where the collarbone meets the sternum, overuse or strain of the chest muscles, and a condition called painful xiphoid syndrome, where the bottom tip of the sternum becomes tender. Slipping rib syndrome, where a lower rib shifts slightly out of place, can also produce pain that seems to come from the sternum area.
Sternal fractures occur in up to 8% of blunt chest trauma cases, most often from car accidents when the chest hits the steering wheel or is compressed by a seatbelt. In people with multiple traumatic injuries involving the chest, the rate rises to about 18%. A fractured sternum causes significant pain with breathing and movement, and it sometimes signals injury to the heart or lungs behind it.
The Sternum in Surgery
For open-heart surgery, surgeons split the sternum down the middle in a procedure called a median sternotomy. This gives direct access to the heart and major vessels. The bone is wired back together afterward with stainless steel wires, and healing takes about eight weeks. During that recovery period, patients are typically told to avoid lifting heavy objects, pushing, or pulling, because those movements stress the healing bone. Full activity usually resumes around three months after surgery.
Anatomical Variations
Not every sternum looks the same. About 9% of people have a small natural hole somewhere in the sternal body or xiphoid process, averaging roughly 5 to 6 millimeters across. Men are more likely to have one (about 12%) than women (about 7%), and prevalence varies across populations. On imaging, these foramina can be mistaken for fractures or bone lesions, so radiologists need to be aware they exist. For most people, a sternal foramen causes no symptoms and is never discovered unless a CT scan or X-ray happens to reveal it.