The cheekbone, technically known as the zygomatic bone, is a paired facial bone that forms the prominence of the cheek and contributes to the structure of the eye socket. This bone is a major component of the midface, and its size and position significantly influence overall facial appearance. Noticing a difference in prominence is common, but faces are almost never perfectly symmetrical. The degree of this difference can range from barely noticeable to distinct, often caused by natural development and long-term habits.
The Baseline Normal Facial Asymmetry
The human body, including the face, is not built with mirror-image symmetry; a slight degree of asymmetry is the universal default state. Studies comparing facial structures consistently show minor, undetectable differences in the underlying bone and soft tissue between the left and right sides. For most people, this natural variation is subtle, and soft tissues like fat and muscle often compensate to mask minor skeletal deviations. This inherent lack of perfect symmetry is a normal product of development. Therefore, noticing a difference in your cheekbones should not automatically be interpreted as a sign of an underlying health problem.
Causes Related to Bone Growth and Structure
Differences in cheekbone size or projection can be traced to inherited factors influencing craniofacial development. Genetics dictates the size, shape, and final positioning of the zygomatic bones through the interplay of multiple gene families. These genes regulate the rate and timing of bone formation and growth during fetal development and childhood growth spurts. These variations mean that one side of the face may grow slightly more or less than the other. Additionally, the way facial muscles attach to the bone can influence its shape. Uneven muscle insertion points or subtle differences in muscle tone can exert different forces, leading to mild asymmetry in the cheekbone structure.
Acquired Asymmetry Through Lifestyle and Habitual Factors
Many noticeable differences in cheekbone prominence develop or worsen over time due to consistent external pressures and habits. A frequent cause is the unconscious tendency to favor one side while chewing, known as unilateral mastication. The muscles on the favored side, such as the masseter, receive more stimulation, leading to muscle hypertrophy, or increased bulk. This makes that side of the face appear fuller and the cheekbone more defined.
This uneven muscle activity places an asymmetrical load on the jaw joint and bones, potentially influencing bone remodeling over decades. Sleeping position is another contributor, as consistently pressing one side of the face into a pillow exerts long-term pressure. This constant compression can affect soft tissue distribution, potentially causing the underlying bone to shift or remodel subtly.
Poor posture, such as a habitual forward head position, can also indirectly affect facial symmetry by altering neck and jaw tension. Dental issues like untreated malocclusion, where the teeth do not align properly, can cause the jaw to shift laterally. This shift alters the alignment of the midface and impacts the perceived height and prominence of the cheekbones.
When Asymmetry Signals a Deeper Issue
While minor asymmetry is normal, a sudden, rapidly progressing, or painful difference in the cheekbones can signal a deeper medical issue. A history of trauma, such as a sports injury or fall that resulted in a zygomatic fracture, can lead to permanent asymmetry if the bone healed imperfectly. Temporomandibular joint (TMJ) disorders, which affect the jaw joints and surrounding muscles, can also cause facial asymmetry accompanied by pain or clicking.
Rare developmental conditions, like hemifacial microsomia, cause one side of the face to be underdeveloped, resulting in significant asymmetry of the jaw, ear, and soft tissues. New or sudden onset of facial drooping or weakness, which may present as cheekbone asymmetry, should be considered a medical emergency, as it can be a sign of a stroke or conditions like Bell’s palsy. If the change in your cheekbone is recent, rapid, or accompanied by functional difficulties like numbness, pain, or limited jaw movement, consulting a healthcare professional is necessary for a full evaluation.