It doesn’t take a PhD in Exercise Science to know that the entire body adjusts to every movement that we make. Things begin to get tricky as we begin to highlight the body’s heavy bias towards the right side.
If you have not already done so, read through this article on the body’s asymmetrical anatomy. You have to know these concepts before fully grasping the rest of this article.
Now that you understand the fundamental differences between the right side and the left side, you can begin to see how the body can get stuck in right single leg stance.
In right single leg stance, your lumbar spine will turn slightly to the right.
One of the major muscles making this movement happen is the right QL. This is why people stuck in this pattern often report right lower back pain.
In this picture you see the ribs have also made a turn towards the right. Because we can't walk around with our chest pointed to the right, our body makes the natural adjustment to re-orient the ribcage to center. This thoracic spine adjustment is driven by the left pectoralis muscle. This is why we typically see individuals with a more developed/tight left pec than right.
There is nothing "wrong" with this position. Problems only arise when we cannot get out of this position (which stems from your asymmetrical anatomy). Fixing this is exactly what the Postural Restoration Institute has pioneered for so many years.
Correcting this, revolves around helping left single leg stance catch up.
IN A NUTSHELL: The lumbar spine turns to the right and the thoracic spine turns back to the left. This is the position of right single leg stance.