What Is the Zygomatic Arch and What Does It Do?

The zygomatic arch is the bony bridge that runs along each side of your skull, connecting your cheekbone to the area just in front of your ear. You can feel it yourself by pressing gently along the ridge beneath your temple. Far from being just a cosmetic feature that gives your face its width, this arch serves as the anchor point for your primary chewing muscles and acts as a structural brace that absorbs and redirects the substantial forces generated every time you bite down.

Where It Sits and What It Is Made Of

The zygomatic arch is formed by two bones meeting in the middle. The front portion comes from a bony extension of the zygomatic bone, which is the main bone of your cheek. The rear portion is a projection from the temporal bone, the large bone that houses your inner ear and forms much of the side of your skull. These two projections overlap and fuse together, creating a continuous bar of bone that curves outward from the skull’s surface. That outward curve is what gives the arch its name and its mechanical advantage: it creates a gap between itself and the skull wall, and your masseter muscle, the thick muscle you can feel bulge when you clench your jaw, passes through that gap on its way from the arch down to the angle of your lower jaw.

A lesser-known portion of the temporalis muscle also originates directly from the zygomatic arch. This zygomatic part of the temporalis runs from the arch to the coronoid process of the mandible, the pointed projection on the upper part of the jawbone where the main temporalis tendon attaches.¹ So the arch is not simply a passive wall for one muscle to hang from. It anchors at least two separate muscles involved in closing and positioning the jaw, making it a true mechanical hub for chewing.

How It Handles the Forces of Chewing

Every time you chew, the masseter and temporalis muscles pull downward and inward on the zygomatic arch with surprising force. Bite force in humans can reach several hundred newtons on the molars, and that force has to travel through bone somewhere. The arch absorbs it, but not uniformly. Research using strain gauges in animal models shows that the front and back portions of the arch experience different loading patterns. During masseter contraction, the front section (the zygomatic bone portion) bends so its lower edge bows outward, with the direction of peak tension running parallel to the pull of the masseter. The rear section (the squamosal/temporal bone portion) bends in the opposite direction, and strain magnitudes there tend to be even larger.²

The arch also experiences different stresses on its inner and outer surfaces. When forces are applied, its outer (lateral) surface tends to be under tension while its inner (medial) surface is under compression, a classic bending pattern similar to what you would see in an engineering beam.³ This matters because bone is not equally good at resisting all types of stress. The shape and thickness of the arch in any given species, or any given person, reflect the specific combination of bending and twisting forces that the bone habitually encounters.

Studies of growing animals add a further wrinkle. In young piglets, the arch does not show the same strain patterns as in adults. The mature bending pattern in the rear portion is essentially absent in piglets, and the alignment of peak tension in the front portion does not yet match the direction of masseter pull. When researchers artificially stimulated the piglet’s masseter with electrodes, the patterns became more adult-like, but the strain magnitudes reached extremely high levels, some of the largest ever recorded in mammalian skull bones.⁴ This tells us that the arch’s bone structure remodels over an animal’s lifetime in response to the actual mechanical loads it experiences, rather than arriving in its final functional form at birth.

Why Shape Varies So Much Across Mammals

Look at a cross section of a zygomatic arch and you will find enormous variety across the animal kingdom. Some species have arches that are nearly cylindrical in cross section, while others have tall, blade-like arches that look more like a fin than a tube. This variation is not random. It directly relates to how much bending and twisting the arch has to resist from the attached chewing muscles.⁵ A cylindrical arch resists forces equally from all directions, which makes sense for a generalist feeder. A tall, thin arch is better at resisting up-and-down bending but weaker against side-to-side forces, which suits an animal whose chewing motion is primarily vertical.

Diet leaves its fingerprint on the arch’s internal structure, too. When researchers compared the zygomatic arches of closely related primate species that eat different foods, they found significant differences in the amount of cortical bone (the dense outer layer) and in the arch’s resistance to bending. Species that eat harder or tougher foods tend to have arches with more cortical bone, particularly in the front portion where masseteric strain is highest.⁶ The arch, in other words, remodels to match the demands placed on it, both within an individual’s lifetime and across evolutionary time.

The position of the arch’s root, the point where it emerges from the face, also shifts with diet. In primates that regularly consume mechanically challenging foods, the arch root tends to sit further forward on the skull. A more anterior root positions the masseter muscle further forward, improving leverage for biting with the premolars and front molars. Comparisons across primate species found this pattern held in the majority of pairs examined, though not universally, since other aspects of skull anatomy and feeding behavior can compensate.⁷

What Happens When Animals Lose It

If the zygomatic arch is so important for chewing, what happens in animals that do not chew at all? Anteaters provide a vivid answer. These animals swallow ants and termites whole, using a long sticky tongue rather than teeth. Over evolutionary time, their zygomatic arch has been partly or completely lost. Giant anteaters and tamanduas have no functional arch, and the masseter muscle (which depends on the arch for its upper attachment) is dramatically reduced. In pygmy anteaters, the jugal bone, one of the bones that normally forms the front part of the arch, is absent entirely, and the deep masseter has disappeared along with it.⁸ Pangolins, another group of ant-eating specialists, show a similar pattern. When the need to chew disappears, the arch becomes expendable, and evolution disposes of it.

This pattern extends beyond mammals. Researchers examining temporal skull openings across land vertebrates argue that the formation of bony bars around these openings, including the arch-like structures equivalent to the zygomatic arch, is driven primarily by where the most forceful biting occurs and whether the animal needs to move resistant food sideways. Forceful biting toward the front of the jaw favors a lower temporal bar, while forceful biting at the back favors an upper one. Species that generate less biting force tend to reduce or lose these bars.⁶ The zygomatic arch is, in this broader evolutionary sense, a structural answer to a mechanical question: how much force do you need to apply with your jaws, and where?

Fractures and Why They Cause More Than Just Pain

Because the zygomatic arch sits exposed along the side of the face, it is vulnerable to direct blows. Isolated arch fractures are a well-recognized injury, and assault is the most common cause by a wide margin. A review of over two hundred patients with isolated zygomatic arch fractures found that roughly 55% resulted from assault, with the average patient being a man in his mid-forties. About four out of five patients were male.⁹

When the arch fractures and collapses inward, it can press against the coronoid process of the mandible or against the temporalis muscle, physically blocking the jaw from opening fully. This condition, called trismus, is one of the key reasons that some arch fractures require surgery rather than just healing on their own. In that same review, patients who ended up needing surgery were far more likely to have trismus and facial numbness (paresthesia) than those managed without an operation. Nearly 80% of all patients, though, were treated without surgery, typically because the fracture was minimally displaced and did not interfere with jaw function.⁹

For fractures that do need repair, several surgical approaches exist. The classic Gillies technique involves making a small incision hidden in the hairline and sliding an instrument beneath the arch to lever it back into place. More complex fractures of the broader zygomatic complex, which can involve the orbital floor and the lateral orbital wall in addition to the arch itself, sometimes require open reduction with plates and screws. A study evaluating combined closed reduction with three-point fixation found better stability than either closed reduction alone or open fixation alone, suggesting that restoring the arch’s position and then securing it at multiple points yields the most reliable long-term result.¹⁰ Another technique using transbuccal instrumentation (working through a small incision inside the cheek) achieved satisfactory cosmetic and functional restoration in over 93% of cases, with average mouth opening improving from about 20 mm before surgery to 40 mm three months after.¹¹

The Facial Nerve Problem

One reason surgeons treat the zygomatic arch with such respect is the facial nerve. The frontotemporal branch of this nerve, which controls the muscles that raise your eyebrows and close your eyelids, crosses directly over the zygomatic arch on its way from the parotid gland region up to the forehead. Damage to this branch during surgery or trauma can leave a person unable to raise the eyebrow on the affected side or fully close the eye, a functionally and cosmetically significant problem.

The nerve crosses the lower edge of the arch roughly 3 cm in front of the tragus, the small flap of cartilage at the front of the ear canal.¹² Another anatomical study found the nerve sitting about 27 mm below the upper edge of the arch in a vertical plane just in front of the tragus, before it courses upward and forward to cross the arch about 19 mm anterior to the tragus.¹³ Surgeons use these measurements as landmarks to avoid the nerve during procedures on the arch, the temple, and even during facelifts. Research on the high-SMAS facelift technique confirmed that the frontal branch remains protected within a deep fascial layer (the parotid-temporal fascia) as it crosses over the arch, which means that careful dissection above this layer can avoid nerve injury.¹⁴

Zygomatic Implants for Missing Teeth

An increasingly common clinical use of the zygomatic bone and arch has nothing to do with fractures. When patients have lost most or all of their upper teeth and the jawbone has severely deteriorated, conventional dental implants may not have enough bone to anchor into. Zygomatic implants solve this by bypassing the wasted upper jaw entirely. These long implants (typically 30 to 50 mm) are angled upward through the remaining maxillary bone and anchored into the dense zygomatic bone at the base of the arch. Because the zygomatic bone is thick, cortical, and well-supplied with blood, it provides a stable foundation even when the upper jaw itself has atrophied to a sliver.

Combining standard implants in the front of the mouth with zygomatic implants in the back has become a reliable strategy for full-arch rehabilitation of the upper jaw. This approach reduces the number of separate surgical stages compared to traditional bone-grafting procedures and shortens overall treatment time.¹⁵ Finite element modeling studies have examined how stress distributes through these implants compared to conventional ones placed in grafted bone, helping surgeons optimize implant placement and design.¹⁶

How the Arch Shapes the Face You See

The zygomatic arch contributes more to facial appearance than most people realize. The width of your face at cheek level is determined largely by how far the arches project outward from the skull. Populations with wider, more laterally projecting arches tend to have broader, flatter-appearing faces, while those with less projection appear narrower. These differences are partly genetic and partly the result of functional loading: people whose diets require more vigorous chewing during growth may develop slightly more robust arches and broader zygomatic regions.

An interesting demonstration of how malleable zygomatic shape can be comes from studies of intentional cranial deformation, a practice carried out in some ancient cultures. When the skull is bound during infancy to reshape the cranial vault, the zygomatic bone does not escape the effects. Research on skulls with different types of deformation found that all deformed groups showed reduced forward projection of the zygomatic bone compared to undeformed skulls, with the degree of change varying by the type and direction of the binding forces applied.¹⁷ This shows that the zygomatic region does not develop in isolation. It responds to mechanical forces transmitted through the growing skull, a principle that also applies in modern orthodontics and orthopedic facial treatments.

Rare Conditions That Affect the Arch

Aside from traumatic fractures, a few uncommon conditions can involve the zygomatic arch. Osteomas, benign bony growths, can develop on the coronoid process of the mandible and grow large enough to press against the inner surface of the arch. In rare cases, an expanding osteoma can actually fracture the zygomatic complex from the inside out, causing progressive facial asymmetry and severely restricted jaw opening. The condition mimics ankylosis (fusion of the jaw joint) and is sometimes called pseudo-ankylosis, since the joint itself is normal but the mechanical obstruction prevents movement all the same.

Congenital conditions that affect zygomatic development include Treacher Collins syndrome and other craniofacial disorders where the zygomatic bones and arches are underdeveloped or absent. In these cases, the cosmetic and functional consequences extend well beyond the arch itself, affecting the orbits, the midface, and the attachment of the chewing muscles. Surgical reconstruction in such patients often involves building up or replacing the zygomatic arch with bone grafts or custom prosthetics, underscoring how central this small bridge of bone is to normal facial structure and function.