Third, opposing excessive lumbar flexion is excessive lumbar lordosis or hyper-extension. Over correcting from a slouched sitting position has drawbacks as well. Sitting with too much lumbar lordosis places additional loading forces to structures that cannot only cause pain, but also degenerative conditions. During hyper-extension of the lumbar spine (think about the low back positions of gymnasts), there is excessive load placed on the facet joints of the back. These are not meant to be weight-bearing structures. Overtime, stress to the facet joints can cause degenerative joint disease with further progression leading to a condition called spondylolisthesis. Generally, this refers to a slippage of the superior vertebrae with respect to the inferior vertebrae. One type is an anteriolisthesis (Figure 29) where the superior vertebrae slips forward relative to the inferior one. The other is the retrolisthesis (Figure 30) where the superior vertebrae slips backward relative to the inferior one.
Figure 29. Anteriolisthesis.
Figure 30. Retrolisthesis.
As excessive lordosis relates to the muscles, they may be in too shortened of a position to be effective in stabilizing the spine. Think of how ineffective it would be to perform bicep curls starting with your elbow half bent and working up. This shortened position of the muscles in a hyper-extended position is inadequate to produce the necessary forces to assist with stabilizing the spine. Additionally, in a hyper-extended lumbar position, the intervertebral foramen, the holes that the nerve roots exit into from the spinal cord, are compromised and made smaller. Therefore, any degenerative or hereditary condition present may further be exacerbated by excessive lordosis. While this position is less common in sitting, it is quite common in standing. Those who stand with excessive lordosis often hang out on the “y” ligaments in the anterior hips, have very inactive abdominal and hip musculature and thereby attain their erect position by sustained passive forces (hip ligaments and loading of the lumbar facet joints). This posture is commonly called the swayback position (Figure 32). After having reviewed 3 postures and their associated pathologies, let’s compare the effects of posture/positioning related to intervertebral disc pressures.
Figure 31. Consequences of the Forward Head Posture.
Figure 32. Swayback Posture.