How to Find the Angle of Louis (Sternal Angle)

The angle of Louis, also called the sternal angle, is a horizontal bony ridge you can feel on the front of your chest where the upper part of the breastbone (the manubrium) meets the longer lower part (the body of the sternum). To find it, slide your fingertip down from the notch at the base of your throat until you feel a distinct bump or step roughly two finger-widths below. That ridge is the angle of Louis, and it sits right at the level of the second rib, making it one of the most reliable surface landmarks on the human body for clinical exams and procedures.

Step-by-Step Palpation

Start at the suprasternal notch, the soft dip between your collarbones at the very top of the breastbone. You can find this easily by running a finger up the center of your chest until it drops into a hollow at the base of the neck. From there, press gently and slide your fingertip straight down along the midline of the sternum. Within a few centimeters, the flat surface of the manubrium will give way to a noticeable ridge or lip that runs roughly horizontally. On many people it feels like a small shelf or speed bump under the skin. That is the sternal angle.

The ridge exists because the manubrium and the body of the sternum meet at a slight forward angle, typically around 160 to 170 degrees in adults. The joint between them is usually cartilaginous, which means it retains a bit of flexibility and tends to stand out as a bump rather than blending smoothly into the surrounding bone. Once you feel it, keep your fingertip on the ridge and slide it laterally to either side. The rib that attaches at that exact level is the second rib. This is the reason clinicians care about the sternal angle: once you have confidently identified the second rib, you can count downward to find the third, fourth, and fifth ribs and their corresponding intercostal spaces.

Why Clinicians Rely on This Landmark

Rib counting sounds like a minor skill, but it underpins a surprising number of clinical tasks. The most common is cardiac auscultation. When a doctor listens to your heart valves with a stethoscope, they place it at specific intercostal spaces, and if they miscount by even one rib, they may be listening in the wrong spot. The aortic valve area, for example, is traditionally assessed at the second intercostal space on the right, which you locate by finding the sternal angle, identifying the second rib, and then dropping one space below it.

Beyond heart sounds, the sternal angle serves as a reference point for placing central venous catheters, inserting chest tubes, and performing needle decompression of a tension pneumothorax. In each of these situations, entering the chest wall at the wrong intercostal space can cause serious harm. The sternal angle is also used in spine surgery as a surface landmark for estimating which thoracic vertebra sits directly behind it. A CT-based study of over a thousand patients found that the vertebral level the sternal angle corresponds to can shift depending on body weight and body mass index, with heavier patients showing a moderate downward shift in the corresponding vertebral level. Patient sex, race, and ethnicity did not change the relationship.

The sternal angle also marks the boundary between the superior and inferior mediastinum, the anatomical compartments behind the breastbone that house the heart, great vessels, trachea, and esophagus. This makes it a dividing line radiologists and surgeons use when interpreting cross-sectional imaging.

When the Sternal Angle Is Harder to Palpate

In a lean person, the sternal angle practically announces itself. In someone carrying more weight around the chest and upper body, the ridge can be buried under subcutaneous tissue. That same large imaging study confirmed what many clinicians already suspected: there is a moderate negative correlation between a patient’s weight and how reliably the sternal angle can be located from the surface. BMI showed a similar relationship. In practical terms, the heavier the patient, the more tissue sits between your fingertip and the bony ridge, and the less distinct the bump feels.

If you are having trouble, try adjusting your approach. Have the person sit upright or lean back slightly against a firm surface. Use two or three fingertips pressed together rather than one, which distributes your touch across a wider area and makes subtle ridges easier to detect. Some practitioners find it helps to start palpating from the sides of the sternum rather than dead center, because the lateral edges of the manubriosternal joint can be more prominent than the midline. You can also try asking the patient to take a deep breath, because the slight movement of the sternum during inspiration can make the joint more perceptible under your fingers.

Anatomical Variation Is More Common Than Textbooks Suggest

Anatomy textbooks present the sternal angle as a reliable, uniform landmark, and for most people it is. But a study of 85 cadaveric sterna found that over 40% had some variation in the size, location, or degree of fusion at the sternal angle.

These variations include a flatter-than-expected angle (so the ridge barely protrudes), an angle that sits slightly higher or lower than the textbook position, and cases where the joint has fused into solid bone, eliminating the distinct bump altogether. A fused manubriosternal joint does not mean the landmark is gone. You can often still detect a faint ridge or line at the former joint site, because even fully ossified joints tend to leave a subtle surface irregularity. But it does mean you should not rely solely on feeling for cartilage “give” at the joint. Some sterna are also slightly asymmetrical, with the ridge more prominent on one side than the other.

The practical takeaway for anyone learning to palpate this landmark: if you cannot find a clear ridge on someone, it does not necessarily mean your technique is wrong. The person may simply have a less prominent sternal angle than average, and you may need to use surrounding landmarks like the clavicles and the first rib to triangulate.

How Aging Changes the Landmark

The manubriosternal joint starts life as a synchondrosis, a cartilage-filled joint that allows a small amount of movement. Over time, some people’s joints gradually ossify, turning the cartilage into bone. This process tends to become more common after the mid-thirties. An autopsy-based study found that manubriosternal joint fusion was absent in younger age groups and became increasingly evident after age 35.

A larger CT-based study of 734 adults found that about a quarter showed complete fusion of the manubriosternal joint. The average age of people with a fully fused joint was 57, compared with 48 for those without fusion. Fusion rates rose progressively with age but topped out around 40 to 44 percent even in the oldest age groups, meaning that complete fusion is never universal, even in elderly adults.

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What does this mean for palpation? In an older adult with a fully fused joint, the sternal angle may feel more like a faint line than a distinct bump. The good news is that even fused sterna usually retain some surface contour at the former joint line. In older patients where the ridge feels indistinct, you can use the second costal cartilage, which attaches right at the sternal angle, as a cross-reference. Feel for the second rib laterally and trace its cartilage medially toward the sternum. The point where it meets the breastbone is the sternal angle, even if you cannot feel the ridge itself.

The Sternal Angle Moves When You Breathe

One detail that surprises many people is that the sternal angle is not a fixed, rigid point. Because the manubriosternal joint retains some cartilaginous flexibility in most adults, the angle changes slightly with every breath. An in-vivo biomechanics study measured this directly and found that the sternal angle varied by an average of about 4.4 degrees over a full inspiratory cycle.

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During a deep breath in, the body of the sternum rocks forward and upward relative to the manubrium. This “pump handle” movement of the upper ribs increases the front-to-back diameter of the chest and draws air into the lungs. The sternal angle is the hinge point for that motion. In conditions that restrict chest wall movement, such as severe emphysema or ankylosing spondylitis, the sternal angle may become more fixed and less palpable as a distinct, flexible joint.

This breathing-related movement can actually help you during palpation. If you rest your fingers lightly over the suspected location and have the person take a slow, deep breath, you may feel a subtle shift or hinge at the joint. That movement confirms you are on the sternal angle rather than on a different surface irregularity.

Common Palpation Mistakes

The most frequent error is starting too low. If you begin palpating partway down the manubrium instead of at the suprasternal notch, you may miss the sternal angle and interpret some other surface irregularity as the landmark. Always start at the notch and work down methodically.

A second common mistake is pressing too hard. The sternal angle is a superficial landmark sitting just beneath the skin, and heavy pressure can actually flatten the soft tissue over it and make the ridge less distinct. Light, steady pressure with the pad of your finger works better than a firm poke. Some clinicians find it useful to use a rolling motion, gently rocking the fingertip side to side across the ridge, rather than pressing straight down.

A third error, specific to clinical exams, is assuming the second rib means the second intercostal space. The second rib itself sits at the sternal angle level. The second intercostal space is the gap just below the second rib. Confusing the two leads to off-by-one mistakes in rib counting, which cascade through every subsequent landmark. When you find the sternal angle, you have found the second rib. Drop one space below it for the second intercostal space, then keep counting downward from there.

Practicing on Yourself

The sternal angle is one of the easier bony landmarks to practice on your own body. Sit comfortably, tilt your head back slightly to expose the neck, and locate the suprasternal notch. Walk your fingers down. On most people of average build, the ridge sits roughly 5 centimeters below the notch, though individual anatomy varies. Once you find it, practice locating the second rib on each side. From there, count down to the fifth intercostal space on the left, which is roughly where the heartbeat is felt most strongly. Being able to do this consistently on yourself builds muscle memory that transfers to examining others.

Studies evaluating palpation accuracy among students in health-related programs have found that anatomical landmark identification is a learnable skill that improves with repetition and shows good reliability once students are trained.

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If you are a healthcare student, practicing on classmates of different body types is especially valuable because it exposes you to the range of variation you will encounter in clinical settings. A person with a barrel-shaped chest from chronic lung disease will feel different from a slender young adult, and both will feel different from a patient with pectus excavatum. Building familiarity with those differences now prevents frustration later.

Conditions That Alter the Sternum

Certain medical conditions can change the shape or position of the sternum enough to make the sternal angle harder to identify. Pectus excavatum, where the breastbone is sunken inward, can shift the sternal angle deeper and alter its relationship with the ribs. Pectus carinatum, where the sternum protrudes outward, can make the angle more prominent but also change the expected rib positions slightly. Previous median sternotomy, the surgical incision used in open-heart surgery, leaves a scar along the midline of the sternum and can distort the surface anatomy, sometimes with palpable wire sutures or irregular bone healing at the manubriosternal joint.

In patients who have had chest radiation, bone changes or fibrosis in the overlying tissue can also make the landmark less distinct. And in rare developmental anomalies like sternal clefts or perforations, the usual bony anatomy may simply not follow the textbook pattern. In all of these situations, the general strategy remains the same: use multiple landmarks together rather than relying on any single one. The suprasternal notch, the clavicles, and the first and second ribs can all cross-check each other when the sternal angle itself is ambiguous.