The ulnar pulse is the rhythmic throb you can feel on the pinky side of your inner wrist, produced by the ulnar artery as it passes close to the skin’s surface just before entering the hand. It sits alongside the far more familiar radial pulse on the thumb side, yet most people have never been asked to find it and many clinicians reach for it only in specific circumstances. The ulnar pulse matters more than its obscurity suggests, playing a role in everything from pre-surgical screening to cardiac catheterization to diagnosing occupational injuries.
Where the Ulnar Artery Runs and Why Its Pulse Lands Where It Does
The ulnar artery begins at the elbow crease, branching off the brachial artery as its larger terminal branch. From there it dives deep beneath several layers of forearm muscle, traveling along the inner (pinky) side of the forearm alongside the ulnar nerve. For most of its journey it is well protected by muscle and tendon, which is why you cannot feel it mid-forearm the way you might feel certain other pulses through thin tissue. Only at the wrist does the artery become superficial enough to palpate, emerging between the tendon of the flexor carpi ulnaris and the tendons of the flexor digitorum superficialis.1PubMed. Anatomy, Shoulder and Upper Limb, Ulnar Artery
To locate the pulse yourself, turn your palm face-up and look at the wrist crease on the side nearest your little finger. The bony bump you can feel there is the pisiform bone, and the ulnar pulse sits just to the radial (thumb-ward) side of that bump, in the soft groove next to the tendon that flexes your wrist inward. Gentle pressure with two fingertips usually picks it up, though it is often fainter than the radial pulse on the opposite side of the wrist.
How the Ulnar Pulse Compares to the Radial Pulse
In day-to-day clinical practice the radial pulse gets almost all the attention. Nurses check it when taking your heart rate, emergency responders reach for it first, and it is the default site for arterial blood gas draws and arterial line placement. The ulnar pulse tends to be checked only when there is a specific reason: before harvesting the radial artery for bypass surgery, during vascular workups of the hand, or when the radial pulse is absent or inaccessible.
Part of the reason is simply that the radial pulse is easier to feel in most people. In one study of patients undergoing cardiac catheterization, the ulnar pulse was graded as comparable in strength to the radial pulse in roughly 69% of patients, weaker in about 16%, and absent (not palpable at all) in another 16%.2Journal of the Saudi Heart Association. Procedural and clinical utility of transulnar approach for coronary procedures following failure of radial route So while most people do have a palpable ulnar pulse, a meaningful minority either have one that is difficult to detect by touch or cannot have one felt at all. That does not necessarily mean the artery is absent; it may simply sit deeper or be smaller in caliber.
The two arteries also differ in how much blood they carry to the hand. In many people the ulnar artery is actually the dominant supplier, feeding the superficial palmar arch that nourishes most of the fingers. The radial artery contributes through the deep palmar arch and by looping into the thumb and index finger. This shared supply is why clinicians care about confirming both are working before they cut, catheterize, or cannulate either one.
The Allen Test and What It Reveals
The most common clinical reason to check the ulnar pulse is the modified Allen test. The idea is straightforward: a clinician compresses both the radial and ulnar arteries at your wrist while you clench your fist to squeeze blood out of your hand. When you open your hand, your palm looks pale. The clinician then releases one artery at a time and watches how quickly color returns. If releasing the ulnar artery restores color within a few seconds, the ulnar supply to the hand is adequate, and it is considered safe to use the radial artery for a procedure (or vice versa).
The Allen test has been a bedside staple for decades, but its accuracy has come under scrutiny. A study comparing Allen test results with actual vessel diameter found no significant correlation between the reperfusion time the test measures and the true size or dominance of each artery. The authors concluded that relying on the Allen test alone to judge hand circulation could increase the risk of problems after procedures that sacrifice one artery.3PubMed Central. Is the Modified Allen’s Test a Useful Tool for Evaluating the Vascular Dominance of the Forearm? On the other hand, earlier work showed that an abnormally long recovery time during the Allen test does predict the absence of flow on Doppler ultrasound, supporting its role as a first-pass screening tool, especially when combined with follow-up Doppler when the result is borderline.4The Journal of Thoracic and Cardiovascular Surgery. Preoperative assessment of hand circulation by means of Doppler ultrasonography and the modified Allen test
In practice, the Allen test remains widely used because it is free, fast, and needs no equipment. But many vascular surgeons and anesthesiologists now treat it as a screening step rather than a definitive answer, following up with ultrasound imaging whenever the stakes are high, such as before harvesting the radial artery for coronary bypass grafting.
Anatomical Variations That Change Where the Pulse Appears
Not everyone’s ulnar artery follows the textbook path. One well-documented variant is the superficial ulnar artery, in which the vessel takes a shortcut by running over the forearm muscles instead of diving beneath them. Reported prevalence ranges from under 1% to as high as 7%, depending on the population studied and the methods used to detect it.5PubMed Central. A rare variant of the superficial ulnar artery, and its clinical implications: a case report When this variant is present, the artery can cross the inside of the elbow right over the bicipital aponeurosis, sitting just beneath the skin. That makes it visible and easily felt, but also dangerously easy to mistake for a vein during blood draws or injections.
Within the superficial ulnar artery variant itself, there is further diversity. Anatomical dissections have documented cases where the vessel arises from different parent arteries and gives off branches at unexpected points. In some individuals the superficial ulnar artery originates from the brachial artery just above the elbow, while in rarer instances it branches from the radial artery instead.6Folia Morphologica. Anatomical variations of the superficial ulnar artery: case series observed on historical specimens prepared by Ludwik Karol Teichmann These differences matter in surgery and vascular access because an artery sitting where no one expects it can be accidentally punctured, ligated, or injected with medication meant for a vein.
For the average person, these variants are harmless and usually go unnoticed for a lifetime. But if you have ever had a nurse comment that your veins look unusual at the elbow crease, or if you have felt a surprisingly strong pulse somewhere on the inner forearm where one “shouldn’t” be, a superficial ulnar artery is one possible explanation.
Hypothenar Hammer Syndrome and Occupational Threats to the Ulnar Artery
The ulnar artery’s final stretch through the wrist passes through a region called the hypothenar eminence, the fleshy pad on the pinky side of your palm. People who repeatedly strike objects with the heel of the hand, such as mechanics hammering with an open palm, carpenters, or cyclists gripping handlebars over long distances, can damage the artery at this point. The resulting condition, hypothenar hammer syndrome, involves thrombosis (clotting) of the ulnar artery from repeated blunt trauma. It is uncommon in the general population but a recognized occupational hazard in workers who use their palm as a tool.7PubMed Central. Ulnar artery reconstruction in hypothenar hammer syndrome with heterotopic placement in carpal tunnel
Symptoms typically include coldness, numbness, or color changes in one or more fingers, usually on the ring and little finger side. In more severe cases, small painful ulcers can develop at the fingertips because the clot blocks enough blood flow to starve the tissue. Checking the ulnar pulse is one of the first clinical steps: if the pulse at the wrist is absent or markedly diminished on the affected hand but present on the other, hypothenar hammer syndrome jumps high on the list of suspects. Confirmation usually requires imaging such as an angiogram or vascular ultrasound.
A related occupational condition, hand-arm vibration syndrome, affects workers who regularly operate vibrating power tools like jackhammers, grinders, and chainsaws. Prolonged vibration exposure can damage the small digital arteries of the hand and may also contribute to clot formation. Screening for arterial blockages has been recommended as part of the workup in affected workers, since vibration may actively promote thrombus development in vulnerable arteries.8PubMed Central. Hand-arm vibration syndrome: A rarely seen diagnosis In these patients, a diminished or absent ulnar pulse at the wrist can be an early clue that vascular damage extends beyond the small digital vessels.
Using the Ulnar Artery for Heart Catheterization
For decades, cardiac catheterization for angiograms and stent placement was done through the femoral artery in the groin. Over the past twenty years, the radial artery at the wrist has become the preferred access point because it causes fewer bleeding complications and lets patients walk sooner. But the radial artery is not always available. It may be too small, previously used and scarred, or needed for a future bypass graft. In those situations, the ulnar artery is a potential backup route.
A meta-analysis pooling five randomized trials with nearly 2,750 patients found that transulnar access carried similar risks of major cardiac events and access-site complications compared to the radial route. The two approaches also took about the same amount of time to complete and used similar amounts of contrast dye.9PubMed. Transulnar versus transradial access for coronary angiography or percutaneous coronary intervention: A meta-analysis of randomized controlled trials The main drawback was a higher rate of crossover, meaning the cardiologist had to switch to a different artery because the ulnar approach failed. That rate was roughly double compared to radial access.
One trial painted a gloomier picture. The AURA of ARTEMIS study, which tested the ulnar artery as a first-line default strategy for coronary procedures, was stopped early because the crossover rate was so much higher that a first-choice ulnar approach was deemed inferior to the radial approach. The researchers concluded that the ulnar route should not be considered an acceptable default alternative to the radial site.10PubMed. Transulnar compared with transradial artery approach as a default strategy for coronary procedures
The takeaway for patients is nuanced. The ulnar artery is a viable backup when the radial artery is off the table, and in experienced hands the procedure itself is safe. But it is not interchangeable with radial access as a routine first choice, mainly because the ulnar artery is harder to cannulate and the success rate of initial puncture is lower. Palpating a strong ulnar pulse beforehand is one factor cardiologists use to decide whether the approach is worth attempting.
Imaging the Ulnar Artery with Doppler Ultrasound
When a simple finger-on-wrist check is not enough, Doppler ultrasound provides a much more detailed view of the ulnar artery. It can measure the vessel’s diameter, the speed of blood flow through it, and whether flow is moving in the expected direction. Clinicians use it before and after arterial cannulation to confirm the artery has not been damaged, tracking changes in cross-sectional area and peak blood flow velocity over days.11PubMed Central. Evaluation of radial and ulnar artery blood flow after radial artery decannulation using colour Doppler ultrasound
Doppler studies have also revealed interesting findings in disease states. In patients with carpal tunnel syndrome, both the radial and ulnar arteries showed significantly higher blood flow volume, peak velocity, and vessel diameter compared to healthy controls.12PubMed. Dynamic Doppler evaluation of the radial and ulnar arteries in patients with carpal tunnel syndrome The likely explanation is that the chronic nerve compression and local inflammation in carpal tunnel syndrome change the local vascular environment. This is not the sort of thing a pulse check at the wrist would ever reveal, but it illustrates how much information flows through the ulnar artery beyond the simple thump of a heartbeat.
Ultrasound is not perfect, though. Simulation work examining how ultrasound measures flow in the radial and ulnar arteries found that clinically significant errors creep in depending on the angle between the ultrasound beam and the vessel. At steeper angles, the overestimation of peak blood velocity can jump from around 10% to 30%, and time-averaged velocity errors can reach 50%.13PubMed. Investigation of Ultrasound-Measured Flow Velocity, Flow Rate and Wall Shear Rate in Radial and Ulnar Arteries Using Simulation For routine clinical decisions these errors are manageable, but they matter when researchers try to draw fine-grained conclusions about small differences in flow between the two arteries.
Wearable Sensors and the Ulnar Pulse
The ulnar artery has attracted interest in the wearable health-tech space as well. Most wrist-based wearables today sit over the radial artery or use general wrist photoplethysmography (PPG) sensors that are not artery-specific. However, some research approaches to cuffless blood pressure monitoring have explored using two in-line PPG sensors placed at known distances along the ulnar and digital arteries. By measuring how quickly the pulse wave travels between the two sensors, the system can estimate arterial stiffness and, from that, derive a blood pressure reading without an inflatable cuff.14PubMed. Adaptive blood pressure estimation from wearable PPG sensors using peripheral artery pulse wave velocity measurements and multi-channel blind identification of local arterial dynamics
This approach is still experimental, but it highlights why the ulnar artery’s anatomy is useful in engineering terms. Its relatively straight course along the ulnar side of the wrist and into the hand provides a clean, linear segment where two sensors can be spaced apart at a reliable distance. The radial artery, by contrast, curves more as it wraps around the base of the thumb. If cuffless blood pressure monitoring matures into a consumer product, the ulnar artery may quietly become one of the most measured pulses in everyday life, even if most wearers never realize which artery is being tracked.
When a Missing Ulnar Pulse Is a Red Flag
A pulse you cannot feel does not always signal a problem. As noted earlier, roughly one in six people simply has a ulnar pulse too faint to detect by touch. Body composition, wrist anatomy, ambient temperature (cold constricts arteries), and even the position of your hand can all affect whether the pulse is palpable on a given day. A calm, warm patient lying down with a relaxed wrist will often have a detectable ulnar pulse that the same patient will “lose” while cold and anxious in a busy emergency room.
That said, a newly absent ulnar pulse on one side, especially when it was present before or when the other wrist still has one, is worth investigating. In the context of finger coldness, numbness, or color changes, it raises suspicion for an arterial blockage such as hypothenar hammer syndrome, an embolus (a clot that traveled from elsewhere), or thromboangiitis obliterans (Buerger disease, a condition linked to smoking that inflames small and medium arteries). Acute loss of a pulse after a wrist fracture or dislocation can signal traumatic arterial injury that needs urgent attention.
For people working in occupations that involve repetitive hand trauma or vibrating tools, periodic awareness of the ulnar pulse can serve as a crude self-check. If you notice persistent tingling, pallor, or coolness in your ring and little fingers, and you can no longer feel the pulse on the inner wrist of the affected hand, mention it to a doctor. Early detection of ulnar artery occlusion gives more options for treatment, including medication to dissolve clots or surgical reconstruction of the damaged segment, before irreversible finger damage sets in.
Carpal Tunnel Syndrome and Unexpected Vascular Effects
Carpal tunnel syndrome is usually thought of as a nerve problem, and it is. The median nerve gets compressed as it passes through the carpal tunnel at the wrist, producing numbness, tingling, and weakness in the thumb, index, and middle fingers. But the vascular changes observed on Doppler in carpal tunnel patients hint at a broader story. The increased blood flow and larger vessel diameters in both the radial and ulnar arteries suggest that the local tissue environment around the carpal tunnel is altered in ways that go beyond nerve compression alone.15PubMed. Dynamic Doppler evaluation of the radial and ulnar arteries in patients with carpal tunnel syndrome Whether these vascular changes contribute to symptoms, result from the same underlying swelling that compresses the nerve, or are simply bystanders is not fully settled. But the finding is a reminder that the ulnar artery, even though it does not pass through the carpal tunnel itself, responds to nearby pathology in measurable ways.
For patients undergoing carpal tunnel release surgery, some surgeons now use preoperative Doppler to map the vascular anatomy at the wrist, partly to avoid inadvertently damaging a variant vessel during the procedure. A superficial ulnar artery, for instance, could lie right in the surgical field. Knowing it is there before the incision matters considerably more than discovering it afterward.