Ideal

• Gaps between elbow/arm and trunk are same on both sides

You See

• Bigger gap on one side between trunk and elbow

Cause

• Short arm abductors – arm is abducted (and/or the arm OS is more adducted, short arm adductors)
• Scapula is downwardly rotated, short scapular downward rotators (and/or the scapula is upwardly rotated to OS, short scapular upward rotators)
• Spine is laterally flexed
• Hip abductors are short on OS