Shoulder dimples are small indentations in the skin that sit directly over the bony tip of the shoulder blade, a structure called the acromion. In most cases, they’re present from birth, completely harmless, and need no medical attention. They can also develop later in life from other causes, though this is less common.
How Shoulder Dimples Form Before Birth
The most widely discussed explanation is mechanical: during development in the womb, the sharp bony point of the shoulder blade presses against the uterine wall, trapping a small amount of skin and tissue between the two hard surfaces. When that pressure releases, the skin remains tethered to the bone underneath, creating a visible dip or dimple on the surface.
This explanation has limits, though. It doesn’t fully account for why shoulder dimples almost always appear symmetrically on both sides, or why they run in families. Both of those patterns point toward a genetic component rather than a purely mechanical one. Researchers have noted that the full mechanism remains unclear, and a molecular or genetic process likely plays a role alongside any physical compression in the womb.
Genetics and Family Patterns
Shoulder dimples are often inherited. Multiple families have been documented where the trait passes from parent to child in a pattern consistent with autosomal dominant inheritance. That means only one copy of the relevant gene variant, from one parent, is enough to produce the trait. If one of your parents has shoulder dimples, there’s roughly a 50% chance you’ll have them too.
In one reported family, a mother, her three-year-old daughter, and her six-year-old son all had bilateral shoulder dimples with no other associated health conditions. Several other case reports have described similar family clusters where multiple members across generations share the trait in isolation, with no signs of any underlying syndrome.
When Shoulder Dimples Signal Something Else
On their own, shoulder dimples are a benign physical variation. However, they also appear as a nearly universal feature of 18q deletion syndrome, a rare chromosomal condition where part of chromosome 18 is missing. They’ve been documented in a handful of other genetic conditions as well, including Apert syndrome and Say syndrome.
The key distinction is whether the dimples appear alone or alongside other physical or developmental differences. A baby born with shoulder dimples and no other unusual features almost certainly just inherited a harmless trait. In the rare genetic syndromes where shoulder dimples appear, they’re accompanied by a constellation of other signs, such as differences in facial structure, growth, or development, that would prompt a clinical evaluation on their own. Isolated shoulder dimples with no other findings warrant no further investigation.
Shoulder Dimpling From Steroid Injections
Not all shoulder dimples are present from birth. People who receive corticosteroid injections in or near the shoulder joint can develop localized dimpling afterward. The steroid causes the layer of fat beneath the skin to shrink, a process called subcutaneous fat atrophy. When enough fat is lost in one spot, the overlying skin sinks inward, creating a visible indentation that can look like a dimple.
This type of dimpling may also come with a lighter patch of skin at the injection site. Skin lightening after a local steroid injection has been reported in roughly 1 to 4 percent of patients. Both the fat loss and the color change are typically gradual, sometimes appearing weeks or months after the injection, and they can be permanent in some cases, though partial recovery over time is possible.
The risk is higher with certain steroid formulations that dissolve slowly and linger in the tissue. Injections placed deeper into joint spaces carry less risk of this side effect than those placed into softer, shallower tissues like tendons or bursae.
Other Causes of Shoulder Dimpling
Beyond congenital and injection-related causes, shoulder dimpling has been linked to infections, metabolic conditions, and trauma. A localized injury that damages fat or connective tissue beneath the skin can leave a permanent indentation as the area heals. Certain metabolic processes that affect fat distribution can also create dimple-like depressions, though these are uncommon in the shoulder specifically.
If you’ve had shoulder dimples for as long as you can remember, or noticed them on your infant, the overwhelmingly likely explanation is the congenital one: a combination of womb mechanics and genetics that left a harmless cosmetic mark. Dimpling that appears suddenly in adulthood, especially after an injection or injury, has a different and usually identifiable cause.