What is Flat Back?

Definition of Flat Back:

Flat back refers to a postural misalignment characterized by a diminished or absent natural curvature of the spine, particularly in the low back. When viewed from the side, individuals with a flat back posture will not display the expected forward curve in the lumbar spine or the slight backward curve in the thoracic spine. With this loss of lumbar lordosis, the spine appears notably straight or flattened. Flatback posture is also commonly referred to as flatback syndrome.

flat back posture syndrome

Anatomy Overview

The spine, also known as the vertebral column, is an elaborate structure consisting of individual bones, or vertebrae, stacked vertically. With the back muscles working synergistically, the vertebrae form a central pillar that supports the body and protects the spinal cord while providing flexibility and movement. The spine is separated into five regions: cervical, thoracic, lumbar, sacrum, and coccyx (from top to bottom). Each region presents a unique curvature to ensure optimal weight distribution, shock absorption, stability, and mobility.

flat back anatomy spinal alignment comparison

Flat back is commonly found with Posterior Pelvic Tilt, but is becoming more common with Anterior Pelvic Tilt with today's disconnected, motion-deprived bodies.

Lumbar Spine

  • Structure: The lumbar region includes the five largest and strongest vertebrae, labeled L1 to L5. They are positioned between the thoracic vertebrae at the upper end and the sacral region at the bottom.
  • Function: This spine section carries the most weight, supporting the upper body and facilitating motions like bending and twisting.
  • Natural Curve: In typical anatomy, the lumbar spine exhibits a concave curve, termed lordosis, when viewed from the side. This inward curve helps in absorbing the stress from body weight and activities. In a flat back posture, this lordotic curve is decreased or lost, causing the lumbar vertebrae to align in a straight fashion.

Thoracic Spine

  • Structure: Situated above the lumbar and below the cervical spine, the thoracic spine contains 12 vertebrae labeled T1 to T12. These vertebrae have points of attachment for the ribs, forming the rib cage.
  • Function: The thoracic spine's primary role is to protect vital organs like the heart and lungs. It also provides structural support and facilitates rotational movements.
  • Natural Curve: The thoracic spine naturally has a gentle outward or convex curve, known as kyphosis. In some flat back scenarios, this kyphotic curve may be decreased, causing the thoracic spine to appear straighter than usual.

Cervical Spine

  • Structure: The cervical region, or neck, is at the topmost part of the spine, consisting of seven vertebrae labeled C1 to C7. The first cervical vertebra, also known as the atlas, supports the skull and permits the nodding motion of the head.
  • Function: The cervical spine supports the head's weight and mitigates jarring forces on the brain. It also allows for a wide range of motions, including side-to-side and up-and-down movements.
  • Natural Curve: Typically, the cervical spine presents a lordotic or inward curve similar to the lumbar region. However, this curve can be diminished or reversed in certain postural misalignments, including flat back.

The spine's normal curvature is vital in maintaining balance, ensuring proper weight distribution, and facilitating movement. Any disruption or alteration, like the flat back posture, can lead to potential musculoskeletal issues and pain. Recognizing these changes early can aid in effectively managing and preventing further complications.

Synonymous Posture Terms 

Flat back posture can also be termed as:

  • Military neck (when referring to the cervical spine)
  • Lumbar flatness
  • Reverse curve
  • Thoracic straightening

The Biomechanics of Flat Back

Skeletal and Muscular Structures

In individuals with a flat back:

  • Lumbar Spine: The lumbar region lacks its natural inward curve. This region's shortened muscles often include lumbar flexors like the rectus abdominis, external obliques, internal obliques, and the psoas major. Lengthened muscles usually encompass the spinal extensors such as longissimus, iliocostalis, multifidi, rotatores, quadratus lumborum, and latissimus dorsi.
  • Thoracic Spine: There's an absence of the usual outward curve. The thoracic region shares many muscular characteristics with the lumbar area due to the interconnectedness of the spine.
  • Cervical Spine: Often described as a military neck, the cervical spine in a flat back condition lacks its typical forward curve. This region's shortened muscles include sternocleidomastoid, anterior scalenes, longus capitis, and longus coli.

Joint Movements

The flattened curvature in the lumbar spine restricts normal joint movements and may lead to limited pelvic and sacral movement. This can result in altered joint mechanics in the spine's adjacent regions as the body tries to compensate for the flatness in one area.

Postural Deviations Found with Flat Back

The absence of natural curves in the spine increases stress on vertebral structures, discs, and surrounding soft tissues. As a result, individuals may develop other postural deviations such as:

What are the Symptoms of Flat Back Posture?

Musculoskeletal pain sciatica

Common Pains and Limitations 

Flat back posture is frequently associated with the following:

  • Lower back pain
  • Neck pain
  • Mid or upper back pain
  • Stiffness and reduced mobility
  • Tight hamstrings and hip flexors
  • Back surgery
  • Difficulty standing upright or with prolonged sitting
  • Muscle tension
  • Fatigue during regular activities

Long-Term Risks and Issues

Continuous neglect of flat back posture can escalate into:

  • Arthritis and joint degeneration
  • Degenerative disc disease or disc herniation
  • Pinched nerves leading to sciatica, leg pain, or numbness
  • Spinal stenosis
  • Osteoporosis
  • Spinal fusion or spine surgery
  • S-I joint complications
  • Vertebral compression fractures
  • Lumbar flat back's effect on pelvic and sacral movement, potentially affecting the entire spinal alignment.

What Causes Flat Back?

flat back posture signs even with yoga

While yoga and other exercise programs have many benefits, posture therapy addresses the misalignments and underlying dysfunctional movement patterns. Here we have someone with joint hypermobility (see the elbows?), and yet the low back cannot flex from the flat back posture. With flat back, the lumbar spine does not extend properly either.

Muscle Imbalances and the Impact of Modern Sedentary Lifestyles

Flat back's emergence often results from an interplay of genetic predispositions, habitual poor posture, muscle imbalances, and certain conditions like ankylosing spondylitis. The intricacies of muscle dynamics play a profound role in dictating the spine's alignment.

The lumbar spine naturally exhibits a slight inward curve called lumbar lordosis. However, prolonged sitting and sedentary lifestyles, becoming increasingly common in our modern world, have altered the typical muscular mechanics surrounding the lumbar region.

For instance, when the body is in a seated position for extended periods, there is an inherent tendency for the pelvis to tilt posteriorly, causing the lumbar spine to flex, which can contribute to a flat back. This posture is exacerbated if one slumps or hunches over, which many do, especially in front of computer screens or mobile devices.

However, an interesting observation in recent times is that despite the predisposition for posterior pelvic tilt during sitting, many individuals present with a neutral or even anterior pelvic tilt combined with a flat lumbar spine. This anomaly can be attributed to the disconnection between the lumbopelvic rhythm. In a functional musculoskeletal system, anterior pelvic tilt typically corresponds with lumbar extension. Still, extended periods of sitting and lack of active lumbar engagement disrupt this coordination, leading to the coexistence of anterior pelvic tilt with a flat back — often accompanied by pain, limited mobility, and functional and structural problems.

Over time, these postural deviations can become ingrained, and the imbalance between elongated and shortened muscle groups further solidifies the flat back deformity. It's a testament to how our evolving lifestyles, dominated by screens and inactivity, can reshape our very skeletal structure.

Posture Terms Related to Flat Back

  • Kyphosis: Refers to excessive outward curve of the thoracic spine, presenting as a hunchback.
  • Scoliosis: A lateral curvature of the spine.
  • Lordosis: Excessive inward curvature of the lumbar spine.
  • Anterior Pelvic Tilt: Tipping forward of the pelvis.
  • Posterior Pelvic Tilt: Tipping backward of the pelvis.
  • Knee Flexion: Bending of the knees.


Flat back isn't merely a benign spinal deformity; it's a precursor to enduring chronic pain, limited movement, and potentially more severe structural problems. Recognizing the signs and delving into the causes of flatback syndrome are crucial steps toward reclaiming your well-being.

Embracing whole-body posture therapy as a nonoperative treatment option can be the transformative key, offering a viable path to restore your spine's natural curve. This proactive approach promotes optimal spinal health and function. It serves as a beacon of hope for those seeking to avoid invasive orthopedic surgeries or the potential side effects of long-term pain medications.

Remember, every step taken toward correcting your posture is a stride forward in your journey to a pain-free, active, and fulfilling life.

Take Control of Your Posture Today!

Don't let flat back hold you back from living a pain-free life. With the right guidance and commitment, you can improve your posture and alleviate associated discomforts. Schedule a Free Consultation & Posture Assessment now and embark on a journey to a healthier spine and a more confident you.

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