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Spondylolysis and Spondylolisthesis

These are separate but sometimes related conditions.

What Is the Difference Between Spondylolysis and Spondylolisthesis?


Spondylolysis is a spinal fracture of a bone structure called the pars interarticularis, which connects the facet joints of the spine. The spinal cord is protected by rings of bone that make up the middle and posterior (rear) portion of the spinal column. In each of these rings, the pars interarticularis (or simply "pars" for short) connects other components of the ring, known as the pedicle and lamina. (See figure 1.)

Spondylolysis (sometimes called by the shortened name, "pars fracture") usually occurs during childhood or adolescence from repetitive stress, rather than from an acute injury. In other words, it is usually a stress fracture rather than a sudden break. This is a common condition of children and teenagers who are involved in organized sports. Active kids and teens with spondylolysis may experience symptoms. However, some people with this condition may not develop symptoms until later in adulthood.

Illustration of the Spinal Column and Location of a Pars Fracture (Spondylolysis)

Illustration: side view of the spinal column
Figure 1: Side view of spinal column

Illustration: Top view of the spinal column
Figure 2: Top view of spinal column


The lower portion of the spinal column is called the lumbar spine. Spondylolysis most commonly occurs in the lower back in the lowest lumbar vertebra (L5). In athletes, this type of injury can be seen when the back is bent backwards repeatedly, in activities such as gymnastics, karate and football. Specifically, this is common in offensive and defensive linemen.

The vertebra initially responds to increased physical strain of such activity by gradually adding new bone cells around the stressed area of the spine. However, an injury can occur too quickly for the vertebra to be repaired, and this leads to a crack in the pars. The crack may affect only one side, but it is not uncommon to have fractures on both sides of the vertebra. When fractures occur on both sides, it is possible for one vertebra to translate or move forward or backward over the neighboring vertebra; this is called spondylolisthesis.

Symptoms of Spondylolysis

Those with a pars fracture may feel pain and stiffness in the lower back that is worsened with activity and improves with rest. Hyperextension (abnormal stretching) of the lower back will usually aggravate the area as it overloads the pars fracture.

Occasionally, nerve symptoms can be present that may include a “pins and needles” sensation in a leg, with or without numbness or weakness in the leg.

  • Pain in the back, neck, legs, thighs or shoulder
  • Muscle spasms or weakness
  • Headache
  • Tingling, numbness and/or stiffness in the back

Diagnosis of Spondylolysis

Evaluation for this condition would include a review of the patient’s medical history and a physical exam, followed by X-rays, which can detect pars fractures.

A bone scan can be used for early detection of a stress fracture of the pars. This involves injecting chemical "tracers" into the blood stream. The tracers then show up on special spine X-rays. The tracers collect in areas of increased metabolism or cell activity in bone tissue, such as would be seen in areas of a stress fracture of the pars interarticularis.

A CT scan may be used to evaluate a pars defect and to visualize healing bone, while an MRI may be useful to assess the surrounding tissue and condition of the disc.

Treatment of Spondylolysis

The treatment for a pars fracture is initially nonsurgical and includes rest and bracing. The fracture can be assessed with a series of X-rays every few months.

Bracing can last for 3 to 4 months while the fracture heals, and physical therapy can also be included to maintain and help strengthen the abdominal and back muscles with specific directed exercises.

If the athlete has persistent pain after nonsurgical treatment, surgery may be required. There are two operations that may be performed:

  1. A laminectomy, which refers to a procedure in which the surgeon removes that portion of the vertebra that includes the pars interarticularis. This is used if there are nerve roots being affected that require decompression.
  2. A posterior lumbar fusion, if a spinal segment has become loose or unstable. A spinal fusion allows two or more bones to grow together, or fuse, into one solid bone. This keeps the bones and joints from moving. Rehabilitation will start six weeks after surgery to allow the bone to heal (fuse). Therapy will usually last for 6 to 8 weeks, and a patient should expect full recovery to take up to six months.


Spondylolisthesis is when spinal vertebrae slip forward over one another. This is often caused when the crack in a pars fracture affects both sides of connection between the lamina and pedicles). In this way, the condition can be a direct result of spondylolysis. However, there is another form of this condition, called degenerative spondylolisthesis. This condition is caused by the deterioration (degeneration) of the facet joints and discs of the spine.

Symptoms of Spondylolisthesis

Symptoms can include:

  • Localized low back pain
  • Pain that radiates down to the legs (if there is associated nerve compression)

Below, find articles and other content for more information about these conditions, as well as a link to HSS doctors who treat them.

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