The “wing bone” in humans is also called the scapula. You may be seeing what’s frequently called scapular winging. This occurs when the inner border of the scapula moves away from the trunk. The presence of scapular winging on both sides suggests a muscle imbalance or weakness.
This is not uncommon in young children, especially boys. It often goes away as the muscles, bones, and joints mature and develop. Scapular winging only on one side may be caused by muscle injury or nerve damage. Single-sided scapular winging should be examined by a medical doctor.