Posture is determined and maintained by coordination of the various muscles that move the limbs; by kinesthetic sense, and by the sense of balance.
A surrounding space provides a stimulus that in turn determines our posture.
The picture below demonstrates the ideal postural alignment where all the loading joints—shoulders, hips, knees, and ankles are aligned at 90 degree angle:
This is what many call a “blue-print” of correct posture alignment—an alignment we all should have, unless we live a motion deprived life.
Importance of Proper Postural Alignment