Scapular push-up
In a push-up position with straight arms, let the chest sink between the shoulder blades, then push the floor away.
3 × 10–12
muscle
From the front of the third to fifth ribs up to the coracoid, a small hook of bone at the front of the shoulder blade.
Tips the shoulder blade forwards and down.
When it is short or busy the shoulder blade sits tipped forward, which leaves less room at the front of the shoulder when the arm is overhead.
In a push-up position with straight arms, let the chest sink between the shoulder blades, then push the floor away.
3 × 10–12
From a relaxed hang, draw the shoulders down away from the ears and hold, arms still straight.
3 × 10–20 s
Other structures the same drills work.
General anatomy, simplified. It describes a structure, not anybody's shoulder, and cannot say what is wrong with yours.