Lumbar lordosis is the natural inward, C-shaped curvature of the lower back. This curve is measured in the sagittal plane (the view from the side) and is fundamental to spinal health. The condition known as “loss of lumbar lordosis,” or hypolordosis, occurs when this natural inward curve is significantly reduced or becomes entirely straightened. This mechanical change disrupts the spine’s normal alignment, often resulting in a forward-leaning posture and significant discomfort.
Postural Habits and Muscle Imbalances
One of the most common factors leading to a flattened lumbar curve is the long-term adoption of unhealthy sitting and standing positions. Chronic poor posture, particularly the slouching often associated with prolonged desk work, forces the pelvis to rotate backward, a movement known as posterior pelvic tilt. This action directly pulls the lower spine out of its inward curve, contributing to a straightened alignment over time.
This postural flattening is intrinsically linked to imbalances in the musculature surrounding the hips and trunk. Tight hamstring muscles, which attach to the pelvis, can mechanically pull the pelvis into a posterior tilt, reducing the lordotic curve. Similarly, overly tight hip flexor muscles can alter pelvic position and limit the motion necessary to maintain the curve.
The necessary support structure for the lumbar curve also fails when the core and gluteal muscles are weak. When the deep abdominal muscles and glutes do not engage effectively, they cannot stabilize the pelvis and lower spine. This muscular weakness causes the spine to rely on passive structures like ligaments, allowing it to settle into a straightened position and leading to a progressive loss of its natural curvature.
Degenerative Changes in the Spine
Structural changes within the spinal column, typically associated with aging and wear, are causes of lordosis loss independent of muscle function. Degenerative disc disease (DDD) is a significant contributor, where the intervertebral discs lose height and cushioning ability. As the discs compress, the space between the vertebrae decreases, which naturally causes the lumbar spine segment to flatten.
This structural collapse reduces the anterior height of the spinal column, forcing the lumbar vertebrae into a straighter profile. Spinal arthritis, or osteoarthritis, can also affect the facet joints located at the back of the vertebrae. The thickening and stiffening of these joint capsules restrict the small movements between spinal segments necessary to maintain the inward curve.
In more severe cases, conditions like ankylosing spondylitis, a type of inflammatory arthritis, can cause the vertebrae to fuse together. If this fusion occurs while the spine is flat, it locks the spine into a permanent state of hypolordosis. This bony fusion eliminates the possibility of movement that might otherwise correct the alignment, resulting in a rigid and flattened lower back.
Surgical History and Flatback Syndrome
A specific cause of lost lordosis is a history of spinal surgery, often resulting in what is clinically termed Flatback Syndrome. This issue primarily arose from older spinal fusion techniques, such as those utilizing Harrington instrumentation to correct scoliosis. These rods were designed to straighten the spine but failed to restore the necessary inward curve in the lumbar region.
Patients who underwent these non-contoured fusions developed a spinal column rigidly straight through the lower back. Because the fused spine could not curve backward to maintain balance, the entire upper body began to lean forward. Certain modern decompression procedures, such as extensive laminecties, can also destabilize the posterior spinal elements, leading to compensatory changes that flatten the lumbar curvature.
How Losing the Curve Affects the Body
The biomechanical consequences of a flattened lumbar spine center on a disruption of the body’s sagittal balance, forcing the center of gravity to shift forward. This forward lean means the body’s weight is no longer distributed efficiently over the pelvis and legs. To prevent falling forward, the back muscles, particularly the paraspinal muscles, are forced to work constantly to pull the trunk backward.
This continuous contraction leads to chronic fatigue and muscular pain, especially when standing or walking. Individuals with significant lordosis loss often exhibit a positive sagittal balance, meaning their head and shoulders fall forward of the hips. They may also bend their hips and knees to compensate and achieve an upright gaze, which places additional strain on the leg muscles and joints.
The absence of the natural curve also compromises the spine’s ability to act as a shock absorber. This results in increased shear forces on the intervertebral discs and facet joints, accelerating degenerative changes and contributing to long-term pain and disability.