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Spinal Stress Fractures and Running - Part 1

Linking Piriformis Syndrome with Low Back Injury

Approximately 80 percent of the population suffers from low back pain at some point in life. Some people are at higher risk for chronic and acute back injuries due to their lifestyles. Athletes are at greater risk of sustaining a lower back injury due to increased physical activity. Strenuous, repetitive and long-term activity, which is common in triathletes, puts a strain on the back that can cause injury to even the finest and most fit athletes. Though the entire spine is used when playing sports, it is estimated that five to 10 percent of all athletic injuries are related to the lumbar spine. Many cases of low back pain in athletes can be traced to a specific event or trauma, while others are brought about by repetitive minor injuries that result in microtraumas.

It is these microtraumas that are problematic for the triathlete. There are many injuries that are associated with running, but anatomical imbalances caused by genetics and/or the repetitive stress and impact forces associated with running can actually cause some of the running injuries that are common in triathletes.

Some triathletes experience low back pain due to running, and while this certainly may be due to muscular fatigue, more times than not it can be associated with a more chronic problem due to anatomical alterations of the spine. This can cause improper hip rotation, possible leg length discrepancy and muscular imbalances, which could lead to overstretching and/or overuse of specific gluteal muscles that are common to running injuries, specifically the piriformis muscle. One of the causes of piriformis syndrome (described later) is spinal stenosis, which happens to be a result of the conditions highlighted below. Thus, it appears that one of the most common running injuries, piriformis syndrome, could actually be linked to a lower back injury that surfaces as a result of genetic predisposition or chronic sport participation. This article will focus on two related lower back conditions, known as spondylolysis and spondylolisthesis, and how specific functional training can improve these conditions in order to lessen the impact or avoid contracting piriformis syndrome.


The most common X-ray identified cause of low back pain is a stress fracture in one of the vertebrae that make up the spinal column, known as spondylolysis. It usually affects the fifth lumbar vertebra in the lower back and is more prevalent in Caucasian males. Research has shown that more than 50 percent of these fractures are actually genetic abnormalities.

To date, there is no definitive cause of spondylolysis. Most physicians agree that the bone defect appears in children most likely due to a genetically weak pars interarticularis teamed with repeated stress to the spine from various physical activities during the major growth years. It is thought that spondylolysis appears in younger and older adults as the result of excessive stress to the spine.

Spondylolysis does not always produce noticeable symptoms. When it does, chronic low back pain is the most common symptom. The pain can stem from mechanical (structural) or compressive (pressure on nerves) pain. The following chart describes the prevalence of spondylolysis in different types of endurance sports.

Sport # of Athletes Polled Spondylolysis % with Spondylolysis
Modern Pentathlon and Triathlon 54 11 20.37
Cycling 95 13 13.68
Water Polo and Swimming 307 34 11.07


If the stress fracture weakens the bone so much that it is unable to maintain its proper position, the vertebra can start to shift out of place, termed spondylolisthesis. This condition occurs when the weakness caused by the spondylolysis causes one vertebra to slip forward over the one below it, resulting in stenosis of the spinal canal. Most cases of spondylolysis in athletes do not lead to vertebral slippage. However, if slippage does occur, it may continue and would need immediate attention.

Many cases are non-symptomatic and do not cause any nerve problems. However, sometimes the slipped vertebra can press into the space belonging to the spinal canal. The neural pressure can lead to low back, buttock and leg pain as well as numbness in the foot. One way to detect spondylolisthesis is to look for physical signs and symptoms including the following:

There are five main causes of displacement and four levels of displacement. The latter is important to understand because it will dictate what type of treatment the athlete should pursue:


Spondylolysis develops most commonly in adolescents, typically in 10 to 15 year olds. The majority of adolescents with spondylolysis do not have symptoms or their symptoms are mild and often overlooked. There is a chance that the deformity with continued stress can lead to the slippage of spondylolisthesis and recurrent low back pain.

It is suspected that spondylolysis occurs in young athletes who are involved in sports that require repeated hyperextension of the lower back. Spondylolysis occurs most frequently in young athletes involved in throwing, gymnastics, rowing, boxing, diving, wrestling, weightlifting, modern pentathlon, triathlon and track and field.

Interestingly, females appear to be more prone to progressive displacement and may need surgical intervention more often than males. Degenerative spondylolisthesis occurs more commonly in females with a 5:1 female-to-male ratio. The incidence increases after age 40.

Older athletes can also develop spondylolisthesis because of degeneration in the disc and the facet joints, which can allow slippage even without a fracture. While it is not known exactly what causes this condition, it is theorized that it probably involves overloading the back part of the facet joints, which can eventually lead to stress fractures.

Risk Factors

There may be a hereditary aspect to spondylolysis as described previously. An individual may be born with thin vertebral bone and therefore be vulnerable to this condition. Significant periods of rapid growth may encourage slippage. In addition, athletes who participate in sports where the lower back is hyperextended at times or during contact sports also may be susceptible. The problem in triathletes lies not only in the terrain (hard versus soft) run on but also the technique of the athlete in the running position. Because some triathletes tend to not focus on maintaining neutral spine (described later), this could cause an excessive hyperextension in the lower back. This combined with the pounding of concrete or asphalt creates an inviting environment for spondylolysis and spondylolisthesis.

As described later, a sound stretching and strengthening program combined with proper running technique that is focused on achieving and maintaining neutral spine is crucial to the prevention of lower back injuries that may be masked by more common running injuries such as piriformis syndrome.


Generally, the athlete will have pain across the low back that may radiate down to the buttocks and may feel more like a muscle strain. The paraspinal muscles will be in spasm, giving a flat appearance to the normally curved lower back. This is mechanical pain. Mechanical pain is due to the actual injury, bony fracture and the related muscle spasms.

Compressive pain can be characterized as radiating. Any pain due to spinal nerve compression will present itself as pain that radiates down the leg. It may also present itself as numbness or heaviness in the leg.

Spondylolisthesis can cause spasms that stiffen the back and tighten the hamstring muscles, resulting in changes to posture and gait. This alteration of gait could significantly affect the triathlete’s ability to run efficiently and economically. In addition, tight hamstrings could be perceived as a separate injury of their own when, in fact, the true causal factor is related to the lower back.

Treatment Options

Initial treatment for spondylolysis is always conservative. The athlete should be encouraged to take a break from training until symptoms go away. Anti-inflammatory medications such as Ibuprofen may help reduce back pain. In most cases, training can be resumed gradually. Stretching and strengthening exercises for the back and abnormal muscles can help prevent future recurrences of pain.

Although mobilization can be done for all levels of displacement, manipulation is never recommended for this condition and must never be conducted. Any level of displacement up to level 4 can be successfully treated non-surgically. Depending on the athlete, anything from grade 2 may require surgical fusion to stabilize the joint. In all cases where non-surgical treatment is possible, the condition is treated symptomatically depending on the spinal areas affected, keeping in mind that the lower or supporting vertebra is always stiffer as a result of the displacement.

In conjunction with treatment, a specific set of exercises (described later) should be prescribed to strengthen the muscles of the trunk. The athlete should never raise his/her legs because this action causes the spine to become elongated. Swimming is beneficial, and running on a soft surface should be emphasized. Surgery may only be needed if slippage continues or if the back pain does not respond to conservative treatment.

Because of the high correlation between spondylolysis and spondylolisthesis with the ever popular triathlete injury, piriformis syndrome, it is important to understand this syndrome and how it relates to and may often be linked to lower back problems.

Piriformis Syndrome

Piriformis syndrome is characterized by pain and instability. The location of the pain is often imprecise, but it is often present in the hip, coccyx, buttock, groin or distal part of the leg. The function of the piriformis muscle is to externally rotate and abduct the thigh. Dysfunction of the piriformis muscle can cause signs and symptoms of pain in the sciatic nerve distribution, that is, in the gluteal area, posterior thigh, posterior leg and lateral aspect of the foot.

Although no general consensus about the etiology and pathophysiology of piriformis syndrome exists, many health professionals attribute this syndrome to a specific mechanism involving the sciatic nerve. Athletes with piriformis syndrome may have the following symptoms:

Possible causes of piriformis syndrome include trauma to the buttocks or gluteal region, anatomical variations of the sciatic nerve and spinal stenosis (described earlier as a product of spondylolisthesis). While piriformis syndrome can arguably be contracted on its own from other causes, the spinal stenosis factor found in spondylolysis and spondylolisthesis can certainly be a causative factor in piriformis syndrome and should always be ruled out during examination.

Part 2 of this series will explore a functional approach to preventing spondylolysis and spondylolisthesis and other lower back injuries that could progress to more common running injuries.


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