Dimples are visible indentations on the skin that often appear during facial movement, most commonly associated with smiling. While they present as a simple surface feature, their origin lies in a subtle variation of the anatomy beneath the skin. Understanding the nature of a dimple requires looking past the surface to the muscles and connective tissues that anchor the skin to deeper structures. Dimples are not caused by bone structure or fat deposits, but rather by unique anatomical connections that pull the skin inward.
The Anatomical Variation Causing Cheek Dimples
The presence of a cheek dimple is primarily due to an unusual configuration of the zygomaticus major muscle, which is the muscle responsible for lifting the corners of the mouth when a person smiles. In individuals without dimples, this muscle typically runs as a single band from the cheekbone to the corner of the mouth. For those with dimples, the muscle often exhibits a structural variation, sometimes described as a double or bifid configuration. This means the muscle splits into two distinct bundles as it travels toward the mouth. The superior bundle inserts at the corner of the mouth in the usual position, but the inferior bundle inserts lower down, often connecting directly to the skin itself. This bifid variation provides the underlying structure that enables the skin indentation to form.
The Mechanism of Subdermal Skin Tethering
The physical appearance of a dimple is a direct result of skin tethering, where the skin is anchored to the underlying facial anatomy. The inferior bundle of the bifid zygomaticus major muscle has a dermal attachment that binds the inner layer of the skin, the dermis, to the muscle tissue below it. When the muscle contracts during a smile, the tension it creates is transferred directly to this attachment point. Because the muscle fibers shorten, the tethered spot on the skin is pulled inward toward the contracting muscle. This creates the temporary depression visible on the cheek, while the surrounding skin remains mobile and smooth.
Dimples Found Elsewhere on the Body
Dimples are not exclusive to the cheeks; other common types exist, each with a different anatomical explanation.
Cleft Chin
A cleft chin, or chin dimple, is often caused by a congenital variation in the underlying bone structure or muscle. The classic Y-shaped cleft results from an incomplete fusion of the two halves of the jawbone, or mandible, during fetal development. The skin over this minute gap is drawn inward, creating the indentation in the center of the chin.
Pebble Chin
A different type of chin dimpling, sometimes called a “pebble chin,” is caused by the overactivity of the mentalis muscle. This muscle attaches directly to the skin of the chin. When it is overused or excessively tense, it pulls the skin tightly, creating a bumpy or uneven texture.
Dimples of Venus
The symmetrical indentations found on the lower back, commonly known as Dimples of Venus, have a non-muscular origin. These dimples are caused by a short, dense ligament that connects the skin directly to the posterior superior iliac spine, a bony prominence of the pelvis. This ligament creates a localized anchoring point on the skin superficial to the sacroiliac joints, distinguishing its cause from the muscular variations seen in facial dimples.