I notice my 9-year old son's shoulder blades stick out. No one else in our family has this problem. Should we do anything about it?

If he isn't complaining of shoulder pain, it's probably nothing to worry about. Children, especially boys before puberty, often have this. It's most likely caused by an under developed muscle called the serratus anterior (SA). The SA is attached to the scapula (shoulder blade) and comes around the ribcage under the armpit. It attaches to the sides of the first eight or nine ribs.

If you think there's something more serious going on, have your doctor check the child. Once the child enters adolescence, the influence of hormones on the muscles will likely strengthen the SA, and the problem will go away. Some people do have a tendency toward
scapular winging into adulthood.

Reference: 

Paula M. Ludewig, PhD, PT, et al. Relative Balance of Serratus Anterior and Upper Trapezius Muscle Activity during Push-Up Exercises. In The American Journal of Sports
Medicine. March/April 2004. Vol. 32. No. 2. Pp. 484-493.

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