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Diagnosing Spondylolysis

Spondylolysis is a stress fracture or break in one of the bones that comprise the spine, called vertebrae. It is one of the most common causes of low back pain in people under age 25. Doctors at NYU Langone’s Spine Center use sophisticated imaging tools to confirm the location of a fracture and determine its severity.

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The spine is composed of 33 vertebrae that stack on top of each other to form the spinal column, which surrounds the spinal cord and nerves. In the back of the spine, the vertebrae are connected by movable joints called facet joints.

Spondylolysis is a stress fracture in a tiny bone, called the pars interarticularis. This is the bony connection between the facet joint and the main part of the vertebra. If this bone weakens or breaks, the vertebra may slip out of place. This condition is called spondylolisthesis.

Causes of Spondylolysis

Spondylolysis usually affects vertebrae in the lower spine, called the lumbar spine, and develops in early childhood. Doctors theorize that some people are born with a weakness in the vertebra, which becomes a stress fracture by age six. In many others, the fracture is thought to occur as a result of trauma.

Children and teenagers who participate in sports that involve repeated backward extensions of the spine—such as gymnastics, pole vaulting, and football—may be at risk for spondylolysis. These activities put extra stress on the lower back and may worsen a stress fracture.

Spondylolysis is more common in boys than in girls, and symptoms often first appear during teenage growth spurts, when the spine is rapidly growing. This period of growth can exacerbate a weakness in the spine or a stress fracture.

In adults, a fracture that occurred during childhood can be aggravated by physical activity, especially movements that bend and twist the spine. In people over 40, age-related degeneration in the spine’s joints and discs, known as osteoarthritis of the spine or degenerative disc disease, may lead to abnormal vertebral motion and pain.

Less commonly, spondylolysis may occur as a result of a severe traumatic injury, such as a car accident. Another possible cause is some metabolic bone diseases, such as osteoporosis or osteogenesis imperfecta, conditions characterized by bones that break easily. They may increase the risk of a stress fracture in a vertebra.

Most people with spondylolysis don’t have any symptoms and live with a stress fracture in the pars interarticularis for years without knowing it. Others experience a persistent ache in the lower back that gets worse during movement. Some people may feel tightness or muscle spasms in the hamstrings, a group of tendons and muscles that run along the back of the thighs.

At NYU Langone, our team of spine specialists includes experts in orthopedics, neurology, neurosurgery, and rehabilitation. Our specialists obtain information about your signs and symptoms in a physical exam, then compare these findings with the results of diagnostic imaging tests. This helps them determine the cause of your back pain and the severity of the injury.

Medical History

A doctor asks about your medical and family history. He or she may ask when you first noticed pain, where it is located, and whether you felt it suddenly after an incident—such as playing a sport or lifting a heavy object—or noticed it gradually.

Physical Exam

Your doctor performs a thorough physical examination to determine the cause of your symptoms. He or she gently manipulates your legs in different extended positions to see if a particular movement causes pain, and presses against the spine to test for tenderness. You may also be asked to bend or walk a few steps so the doctor can assess hamstring tightness and determine whether there are any problems with your gait, balance, or ability to move.


Doctors use X-ray imaging to take detailed pictures of your spine. X-rays can reveal a stress fracture in the pars interarticularis. An X-ray may be all a doctor needs to diagnose spondylolysis.


Your doctor may recommend an MRI to further explore the source of your lower back symptoms. An MRI uses a magnetic field and radio waves to to create computerized, three-dimensional images of your spine and the surrounding soft tissues, such as nerves and muscles.

A doctor may use an MRI to look for swelling in a spinal bone, which may indicate a fracture. Often, an MRI is the first diagnostic test used with or without an X-ray in assessing back pain and possibly diagnosing spondylolysis.

CT Scan

If there is evidence of a stress fracture on an X-ray but your doctor needs to see the bones in more detail, he or she may recommend a CT scan. A CT scan uses X-rays and a computer to create two- and three-dimensional images of the spine from a variety of angles, giving doctors more comprehensive information about a possible fracture.

Bone Scan

Your doctor may recommend a bone scan to determine whether a fracture in a vertebra is actively healing or the result of an old injury.

First, a technician injects a small amount of a dye into a vein in your arm. This dye, called a tracer, travels through the bloodstream and accumulates in places where your cells and tissues are making repairs.

After several hours, a radiologist scans your body using a special camera designed to capture images of the tracer. If it accumulates in the site of a fracture, this may indicate that the injury is actively healing.

Diagnostic Injection

If the origin of your back pain is difficult to diagnose, your doctor may recommend an injection of an anesthetic into the area of the pars interarticularis. If the injection causes the pain to go away for a few hours, it may indicate spondylolysis.

Our Research and Education in Spondylolysis

Learn more about our research and professional education opportunities.