Full Ball & Socket Joint Description. [Continued from above] . . . In the shoulder joint, the spherical head of the humerus (upper arm bone) fits into the glenoid cavity of the scapula (shoulder blade). The glenoid cavity is a small and shallow cavity that permits the shoulder joint the greatest range of motion in the human body.
Lumbar lordosis refers to the inward curvature of the spine just above the buttocks. The National Institutes of Health reports that lordosis is caused by spondylolisthesis. Spondylolisthesis is a condition in which a spinal bone slips out of its normal space and onto the bone below it.
The hypertonicity of the psoas muscle has a tendency to flex the lumbar spine, causing the lumbar spine to diminish in lordosis especially when a weakness of the erector spinae is present. The muscles involved in hip extension and abduction can be divided into two groups, postural and phasic (Table 1).he three muscles are the gluteus maximus(primary mover/agonist), biceps femoris(synergist) and erector spinae(synergist). Any deviation from the specific muscle activation is considered an altered movement pattern. This will cause hip extension dysfunction, muscle imbalance, pain and contribute to changes in posture.