A larger-looking butt can sometimes reflect posture, not body shape. Researchers say this posture change appears more often in autism and ADHD.

The posture pattern behind a “duck butt”

First, the issue is often an anterior pelvic tilt. That means the pelvis tips forward instead of staying level. This tilt increases the lower-back curve and makes the belly and glutes stick out. Anyone can have it, but studies link it to autism and ADHD in children.

Why it may happen in these kids

Next, many children with autism or ADHD have low muscle tone. That can leave the core and glutes too weak to hold the pelvis in place. Sitting for long periods or toe walking can also tighten hip flexors and the lower back. These changes can make posture harder to control during movement.

What studies have found

Also, one study used 3D motion analysis and found children with autism walked with a more forward-tilted pelvis. They also pushed off less with their ankles and bent their hips forward more. Another study found boys with ADHD had a pelvic angle about 4.5 degrees higher than peers. Experts warn the tilt can cause back, hip, or knee pain.

Finally, stretching hip flexors and strengthening the core and glutes can help. Exercises like bridges, planks, leg lifts, and wall sits may improve alignment. Therapists can tailor plans for children, including sensory needs.