Xiphoid process

The xiphoid process is the small, pointed lower end of the breastbone (sternum). The sternum has three parts, the manubrium at the top, the body in the middle and the xiphoid process at the bottom, and the xiphoid is the smallest. Its name comes from the Greek xiphos, a straight sword. It is roughly 2 to 5 cm long, with its tip at about the level of the tenth thoracic vertebra, and it joins the body of the sternum at the xiphisternal joint (Anderson et al., 2023).

At birth the xiphoid is made entirely of cartilage. It gradually turns to bone with age, but the age at which this happens varies widely (Anderson et al., 2023).

What does the xiphoid process do?

It is an anchor point. At the front, the linea alba, the tendinous seam down the middle of the abdomen, and fibres of the rectus abdominis attach to it. At the sides it receives the sheet-like tendons of the three flat abdominal muscles: the external and internal obliques and the transversus abdominis. At the back, fibres of the diaphragm, the main breathing muscle, and of the transversus thoracis attach, along with the costoxiphoid ligaments that tie it to the rib cartilages (Simpson & Hawken, 2007).

So although it is small, the xiphoid sits where the abdominal wall, the rib cage and the diaphragm meet. The tissues attached to it are richly supplied with nerves, mostly the lower intercostal nerves, with the phrenic nerve serving the diaphragm (Simpson & Hawken, 2007).

Why the xiphoid process varies so much

Its shape varies a great deal between people. In CT scans of 500 adults (Akin et al., 2011):

• the xiphoid angled forwards in 65.4% and ran in line with the sternum in 33.2%
• it ended in a single point in 62.6%, two points in 32.8% and three in 4.6%
• it had fully turned to bone in only 50.8%
• 43% had at least one small hole (foramen) through it

A larger study of 902 patients and 41 cadavers found pointed, oval and forked shapes in 45%, 41% and 14% respectively, and a foramen in 58% (Xie et al., 2014). The exact figures differ between studies, but both show that an unusual-looking xiphoid is common.

Is the lump below my breastbone the xiphoid process?

Often it is. Because the xiphoid points forwards in most people, its tip can be felt as a hard, fixed point under the skin. The NHS advises seeing a GP about a lump if it gets bigger, is painful, red or hot, or is still there after 2 weeks, or if you’re worried (NHS). A GP will look at it and may be able to tell you what is causing it.

The xiphoid process at a desk

For most people the xiphoid causes no trouble at all. Repeated pressure can matter for the few who develop a tender xiphoid: one reported case was a carpenter who, for years, pushed wood into a cutting machine with it held against his chest. His symptoms eased with anti-inflammatory medicine and advice to avoid that pressure (Yapici Ugurlar et al., 2014). If you find yourself leaning your upper abdomen into the edge of the desk, it is worth looking at how your chair is set; see office chair setup. Pain from the xiphoid itself is covered under xiphodynia.

When to see a doctor

Pain at the bottom of the breastbone can come from the heart or the stomach as well as from the chest wall. Call 999 if you have sudden chest pain or pressure that doesn’t go away, pain that spreads to your arms, neck, jaw, stomach or back, or chest pain with sweating, feeling sick, light-headedness or breathlessness. See a GP for chest pain that comes and goes (NHS).