When the shoulder blade pokes out and does not lay flat on the surface of the upper back, we call it scapular winging. This is usually caused by weakness in the muscles that externally rotate and retract the scapula.
Our current lifestyles usually include too much time working on the computer and driving. These are probably the two biggest contributors to the forward posture that weakens the muscles which lead to scapular winging.
While it is unrealistic for many to reduce or limit their time on the computer or behind the wheel, it is plausible to introduce a few exercises to combat the effects of this bad posture-inducing behavior.
Get on the floor into the standard pushup position but instead of lowering your entire body towards the floor, lock your elbows and pinch only your shoulder blades together. Next, round your upper back out by separating your blades. Your body should sink and rise slightly while performing this exercise. Keep your abdominals engaged and be sure not to let the curve of your lower back increase.
Grasp a light resistance band overhead with hands shoulder-width apart. Squeeze your scapulae down and back tightly, and then bend your elbows to about 90 degrees. Hold for a few seconds then repeat.
Start with your arm raised to 90 degrees at your side with elbow bent to 90 and forearm parallel to the floor. Hold a light weight (1-2 lbs.) and slowly rotate your forearm up towards the ceiling, stopping when forearm is perpendicular to the floor. Slowly return to starting position and repeat.
Perform 1 set of 10-12 repetitions of these exercises every other day, increasing to 2 or 3 sets gradually and with no pain. Being consistent with these will reduce existing scapular winging and prevent potential new onset.