Posture, which is the relative disposition of the body at any one moment, is a composite of the positions of the different joints of the body at that time. The position of each joint has an effect on the position of the other joints. Ideal postural alignment (viewed from the side) is defined as a straight line (line of gravity) that passes through the earlobe, the bodies of the cervical vertebrae, the tip of the shoulder, midway through the thorax, through the bodies of the lumbar vertebrae, slightly posterior to the hip joint, slightly anterior to the axis of the knee joint, and just anterior to the lateral malleolus. Correct posture is the position in which minimum stress is applied to each joint. Upright posture is ideal, where minimal muscle activity is needed to maintain that position.
Faulty posture is any position that increases the stress to the joints. Pathology will commonly arise from faulty posture. Pathology may be the result of repeated small stresses over a long period of time or of constant abnormal stresses over a short time span. These chronic stresses can result in the same problems that are seen with an acute severe stress causing excessive wearing of the articular surfaces of joints. The soft tissue (muscles, ligaments, tendons, etc. ) may become weakened, stretched, or traumatized by the increased stress. These stresses eventually lead to injury, pain, and abnormalities.
There are many causes of poor posture. Some are postural (positional) and some are structural. The most common postural problem is a poor postural habit; for whatever reason, the patient does not maintain a correct posture. This is often seen in people who sit or stand for extended periods of time and begin to slouch. The presence of pain may also cause postural deformities. The majority of postural non-structural problems are able to be reversed. Treatment involves strengthening weak muscles, stretching tight structures, and teaching the patient that is is his/her responsibility to maintain a correct upright posture in standing, sitting, and other ADLs.
Structural deformities, which include congenital abnormalities, developmental problems, trauma, or disease also cause faulty posture. These deformities mainly involve the bony structures which make rehabilitation more challenging. However, patients can often be relieved of pain and slow down degenerative changes with proper postural instruction from a physical therapist.