The Lumbar Spine Anatomy and Function (2025)

The lumbar spine includes the five vertebrae in your lower back numbered L1 to L5. These bones help provide mobility and stability to your back and spinal column and are an attachment point for many muscles and ligaments.

The lumbar region is located between the thoracic (chest) region of the spine and the sacrum, a large bone at the base of the spine. The lumbar spine usually curves slightly inward, called lordosis. Problems with the lumbar spine may cause pain and limited motion in your back or hips.

Anatomy of the Lumbar Spine

In a normal, healthy spine, the five lumbar vertebrae stack on top of one another in a centered alignment. While all vertebrae have approximately the same shape, the lumbar bones are the largest. This is because they carry a larger load transmitted from the top of the head down to the lower spine.

Another reason why the lumbar bones are larger than the cervical and thoracic vertebrae is that they must be large and strong to support the surrounding muscles and upper body bones during movement.

The back of the vertebra is more complicated, with protrusions and valleys, each with a purpose integral to the spine. The bone extends out from the back of the vertebra to form canals for nerves, joints for stability, and attachment sites for muscles. These parts of the spine include:

• Spinous process
• Transverse process
• Facet joint
• Lamina
• Pedicle
• Pars interarticularis

Each region of the spine has a directional curve associated with it. The lumbar spine has a slight forward curve called a lordotic curve. This curve helps keep the discs and muscles in proper alignment.

The lumbar spine rests upon the sacrum. The place where they meet is called the lumbosacral joint, or L5-S1.

Muscles

The muscles in your lower back work with your abdominal muscles to move your torso and lower back. These muscles include:

• Latissimus dorsi
• Iliopsoas
• Paraspinals
  

Discs

Above and below each vertebra is an intervertebral disc. The disc serves as a shock absorber between each lumbar bone. It also helps support your body weight and allow movement between each vertebra.

Ligaments

The ligaments in your lumbar spine help with smooth motion of your lumbar spine and keep it stable. These include:

• Anterior longitudinal ligament
• Posterior longitudinal ligament
• Supraspinous ligament/interspinous ligament
• Ligamentum flavum
• Intertransverse ligament
• Iliolumbar ligament

Spinal Cord

The spinal cord is the bundle of nerve tissue that extends from your brain and runs down your back to the L1 vertebra. The spinal cord is responsible for sending messages between your brain and muscles.

Nerves

Nerves branch off of the spinal cord at the right and left sides of the vertebrae in your lower back. These nerves control pain signals and movement in your lower limbs. They include L1 to L5 spinal nerves.

Blood Vessels

Your lumbar spine area also contains blood vessels, which branch from the large abdominal aorta. These blood vessels supply the vertebrae, muscles, and ligaments of your lumbar spine.

Function

The lumbar area of the spine is the physical center of the body. This area is the hub for many basic activities, including balance and the generation of locomotion (walking and running, etc.) Some of the lumbar spine's most important functions include:

• Supporting the body's weight: The lumbar vertebrae and discs take the load coming down the spine.
• Protecting lumbar nerve roots: These nerves travel from your spinal cord to your buttocks and legs. The lumbar bones have canals where the nerves are protected.
• Acting as an attachment point for muscles: The latissimus dorsi, the iliopsoas, and the paraspinals all attach at various points of the lumbar bones, helping to move them.
• Moving the body: The lumbar spine helps with flexion and extension (front-to-back movement), side bending, and rotation of your trunk. These movements are performed by the muscles of the lower back and may vary depending on strength and flexibility.

Conditions

Many conditions can cause pain around the lumbar spine. These include:

• Lumbar stenosis
• Spondylolisthesis
• Herniated disk
• Vertebral compression fracture
• Pinched lumbar nerve (lumbar radiculopathy)
• Muscle spasm
• Degenerative disc disease

Symptoms of a lumbar spine problem may include:

• Back pain
• Hip, thigh, or leg pain
• Loss of back mobility
• Weakness in your back, hip, or leg
• Numbness or tingling in your hip, thigh, or leg

If you have any of these symptoms, you should see a healthcare provider right away. They can diagnose your condition and get you the right treatment.

Diagnosis

If you have pain or other symptoms in your lower back, your healthcare provider may recommend imaging tests and/or electrodiagnostic tests to help diagnose the condition. These may include:

• Computed tomography scan (CT scan)
• Magnetic resonance imaging (MRI)
• X-rays
• Electromyogram (EMG)
• Myelogram

Treatment

The best treatment for a lumbar spine condition will vary depending on the condition, its severity, and your overall health. Both surgical and non-surgical options may be considered.

Nonsurgical

Treatment for lumbar spine problems usually involves a combination of stretching and strengthening exercises. These exercises may include:

• Lumbar press ups
• Pelvic tilts
• Lumbar flexion
• Sciatic nerve stretches
• Lumbar stabilization exercises

Working with a chiropractor or physical therapist can help ensure you do the right things for your spine. Your specialist can also show you how to maintain proper posture to help prevent future problems with your lumbar spine.

Most episodes of back pain resolve within a few weeks of onset. You can expect to be back to normal within a month or so. If your symptoms persist, you should check in with your healthcare provider; you may require other treatments such as injections or surgery for your lumbar spine.

Understanding the basic anatomy of the five lumbar bones that make up your low back can help you get the right treatment and care for your back.

Surgical

Some conditions may require surgery. There are a few different types of lumbar spine surgery, including:

• Lumbar spinal decompression surgery: The goal of this surgery is to reduce symptoms caused by pressure on the spinal cord or nerves. The surgeon may use one of several techniques, including removing part of a disk, removing bone spurs, extending the openings around the nerve root, or removing part of the front portion of the vertebra.
• Lumbar disk replacement surgery: This procedure involves removing the disk and replacing it with an artificial one.
• Lumbar spinal fusion: This procedure permanently connects two or more of the lumbar vertebrae to eliminate the motion between them.
  

Summary

The lumbar spine includes the five vertebrae in your lower back. Muscles, disks, ligaments, nerves, and blood vessels also help support your lumbar spine and facilitate movement and stability in your lower back.

Many conditions can cause pain in the lumbar spine, including lumbar stenosis, fracture, degenerative disc disease, and others. Surgical and non-surgical treatments can help reduce pain and improve mobility and function.

By Anne Asher, CPT
Anne Asher, ACE-certified personal trainer, health coach, and orthopedic exercise specialist, is a back and neck pain expert.