- Spondylolysis is a stress fracture in the lower back, commonly affecting young athletes due to repeated spinal hyperextension.
- When spondylolysis causes pain, targeted physiotherapy and strengthening often lead to a full return to activity.
- Repeated hyperextension of the lower back, common in sports, is the primary cause of this stress fracture.
- Bilateral spondylolysis can cause vertebral slippage, called spondylolisthesis, which your doctor will monitor closely.
Table of Contents
- Anatomy of the Pars Interarticularis
- Why L5 is Most Affected
- Relationship with Spondylolisthesis
- Causes and Risk Factors
- Mechanism of Injury
- At-Risk Sports
- Risk Factors
- Symptoms
- Asymptomatic Spondylolysis
- Symptomatic Spondylolysis
- Warning Signs
- Diagnosis
- Clinical Examination
- Imaging
- Classification
- Conservative Treatment
- Phase 1: Relative Rest (0-6 weeks)
- Phase 2: Physiotherapy and Strengthening (6-12 weeks)
- Phase 3: Return to Sport (12-24 weeks)
- Criteria for Return to Sport
- When Surgery Is Necessary
- Surgical Options
- Prevention
- Frequently Asked Questions (FAQ)
- Does spondylolysis heal completely?
- Can you play sports with spondylolysis?
- What is the difference between spondylolysis and spondylolisthesis?
- Is a brace always necessary?
- Does spondylolysis always cause back pain?
- Are my children at risk if I have spondylolysis?
Spondylolysis
Spondylolysis is a defect (stress fracture or discontinuity) of the vertebral pars interarticularis, which is the portion of bone connecting the superior and inferior articular facets. It predominantly affects the fifth lumbar vertebra (L5) in 85% of cases and the fourth (L4) in 10%. It is one of the most common causes of low back pain in young athletes, with a prevalence in the general population of 3-6% and up to 30-50% in athletes practicing sports with repeated hyperextension (artistic gymnastics, diving, weightlifting).
Spondylolysis is often asymptomatic and discovered incidentally, but when it causes pain, a targeted program of physiotherapy and muscle strengthening allows a complete return to activity in 80-90% of cases without the need for surgical intervention.
Anatomy of the Pars Interarticularis
The pars interarticularis (or vertebral isthmus) is a thin portion of bone located between the superior and inferior articular processes of each vertebra. It functions as a “bridge” that keeps the articular facets aligned and contributes to segmental stability.
Why L5 is Most Affected
- The lumbosacral junction (L5-S1) is the point of maximum mechanical stress on the spine: compression, shear, and torsional forces converge here.
- The angle of inclination of the sacrum generates an anterior shear force that tends to cause L5 to slip forward on S1.
- The pars of L5 is anatomically thinner and longer than other vertebrae.
- During hyperextension, compressive forces on the posterior pars increase 5-6 fold.
Relationship with Spondylolisthesis
When spondylolysis is bilateral (affecting both sides of the same vertebra), the posterior bony constraint is lost, and the vertebra can slip forward on the one below: this condition is called isthmic spondylolisthesis. 50-80% of bilateral spondylolyses evolve into grade I-II spondylolisthesis.
Causes and Risk Factors
Mechanism of Injury
Spondylolysis is a stress fracture caused by repeated microtrauma to the pars interarticularis. It is not a congenital malformation, as previously believed, but develops during growth due to repeated mechanical stresses.
The main mechanism is repeated hyperextension of the lumbar spine, often combined with rotation. During extension, the inferior articular facets of the superior vertebra compress the pars of the inferior vertebra, creating concentrated stress.
At-Risk Sports
- Artistic gymnastics: prevalence up to 30-50% (repeated hyperextensions)
- Diving: hyperextension during water entry
- Weightlifting: axial loads in extension
- Soccer: hyperextension during kicking
- Cricket/baseball: bowling and throwing with rotation and extension
- Dance: arabesque and extension movements
- Swimming (butterfly and dolphin): repetitive lumbar undulation
Risk Factors
- Age: the peak incidence is between 10 and 16 years, during the pubertal growth spurt (the pars is more vulnerable during rapid growth)
- Male sex: M:F ratio of 2:1
- Competitive sports involving extension
- Lumbar hyperlordosis: increases stress on the pars
- Spina bifida occulta: increases the vulnerability of the L5 pars
- Family history: increased risk in first-degree relatives
Symptoms
Asymptomatic Spondylolysis
Up to 50% of cases of spondylolysis are completely asymptomatic and are discovered incidentally during radiological investigations for other reasons. The presence of asymptomatic spondylolysis does not require any treatment.
Symptomatic Spondylolysis
- Low back pain: dull, deep, localized in the lower lumbosacral region, generally unilateral
- Pain accentuated by extension: pain typically increases when leaning backward, especially with ipsilateral rotation
- Pain during sports activity: manifests during practice and improves with rest
- Absence of radiculopathy: isolated spondylolysis rarely causes sciatica or neurological deficits (unlike disc herniation)
- Lumbar stiffness: sensation of tension in the lower lumbar region
- Hamstring contracture: reflex spasm of the posterior thigh musculature, present in 50-80% of cases
Warning Signs
Consult your doctor or physical therapist if you experience:
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- Pain radiating down the leg (possible spondylolisthesis with radicular compression)
- Muscle weakness in the lower limbs
- Urinary or bowel disturbances
- Night pain that does not respond to changes in position
Diagnosis
Clinical Examination
- Palpation: tenderness to pressure on the midline in the L4-L5 or L5-S1 region
- Single-leg hyperextension test (Stork test): the patient balances on one leg and hyperextends the spine; the appearance of ipsilateral low back pain is suggestive of spondylolysis (sensitivity 73%)
- Mobility assessment: lumbar extension is typically painful
- Hamstring test: frequent shortening
- Neurological examination: typically negative in isolated spondylolysis
Imaging
- X-ray: AP, lateral, and oblique views. The oblique view may show the classic “scotty dog with a collar” sign of Lachapèle (interruption of the pars). However, the sensitivity of X-ray is only 33% for acute lesions.
- CT (computed tomography): is the most accurate examination for visualizing the pars fracture and classifying it (active, healing, pseudoarthrosis). Sensitivity > 95%.
- MRI (magnetic resonance imaging): can show bone edema of the pars (acute/active phase fracture) and evaluate neural structures. Useful for distinguishing recent lesions from pseudoarthrosis.
- Bone scintigraphy/SPECT: high sensitivity for active lesions (stress fractures in the metabolic phase).
Classification
| Stage | Description | Healing Prognosis |
|---|---|---|
| Acute (stress reaction) | Bone edema without visible fracture line | Excellent (healing in 6-12 weeks) |
| Active fracture | Fracture line with bone edema | Good (healing in 3-6 months) |
| Chronic fracture | Fracture line without edema | Moderate (bone healing unlikely) |
| Pseudoarthrosis | Consolidated bone defect with sclerotic margins | Bone healing not expected |
Conservative Treatment
The pars interarticularis is a thin bony bridge between vertebral articular processes that maintains spinal alignment; when fractured, it causes localized lower back pain worsening with extension, particularly at L5-S1. Conservative treatment is effective in 80-90% of cases and always represents the first approach.
Phase 1: Relative Rest (0-6 weeks)
- Suspension of sports activity that caused the injury
- Lumbosacral brace: a rigid anti-lordotic brace (Boston overlap type) is indicated in active fractures to reduce stress on the pars. It is worn for 6-12 weeks (depending on severity). Evidence is moderate, but many specialists recommend it for acute fractures.
- NSAIDs: for pain control in the acute phase
- Unloaded aerobic activity: swimming (no butterfly), upright stationary cycling
Phase 2: Physiotherapy and Strengthening (6-12 weeks)
Once the pain subsides, the rehabilitation program begins with your doctor or physical therapist:
Core Stabilization
- Front plank: 3 sets of 20-30 seconds, progressing up to 60 seconds
- Side plank: 3 sets of 15-20 seconds per side
- Dead bug: supine, alternate extending opposite arm and leg while maintaining a neutral spine. 3 sets of 10
- Bird-dog: on all fours, same alternation. 3 sets of 10
- Abdominal hollowing: activation of the transversus abdominis in a neutral position
Hamstring and Hip Flexor Stretching
Stretching these muscle chains is fundamental:
- Hamstring stretch: supine with resistance band, leg extended towards the ceiling. 3 x 30 seconds per side
- Iliopsoas stretch: kneeling lunge with pelvic retroversion. 3 x 30 seconds per side
- Quadriceps stretch: in a side-lying position, bring the heel to the glute. 3 x 30 seconds per side
Muscle Strengthening
- Glute bridge: 3 sets of 15, progressing to single leg
- Clamshell with resistance band: 3 sets of 15 per side
- Wall sit: 3 sets of 30 seconds
- Lateral step-up: 3 sets of 10 per side
Phase 3: Return to Sport (12-24 weeks)
- Gradual progression of specific activity
- Proprioception and neuromuscular control training
- Technical modifications: correction of athletic movements that caused the overload
- Maintenance program: core stabilization exercises should continue indefinitely
Criteria for Return to Sport
- Absence of pain during activity
- Full and pain-free lumbar mobility
- Symmetrical and adequate core strength
- Completion of a sport-specific re-athleticization program
- Imaging showing healing or stabilization of the lesion
When Surgery Is Necessary
Surgery is indicated in 10-20% of cases, when:
- Failure of conservative treatment after 6-12 months
- Progressive spondylolisthesis (slippage > grade II)
- Neurological deficits (rare in isolated spondylolysis)
- Persistent and disabling pain that limits daily activities
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Surgical Options
- Direct pars repair (Buck’s technique, Scott’s technique): fixation of the fractured pars with screws. Indicated in young patients with spondylolysis without spondylolisthesis and an intact disc.
- Posterolateral fusion (L5-S1): indicated when associated spondylolisthesis or disc degeneration is present.
- Post-operative rehabilitation requires 4-6 months with a progressive strengthening program.
Prevention
- Training periodization: avoid excessive volumes of extension activities, especially during the growth spurt.
- Core strengthening: preventive program in all at-risk sports.
- Correct technique: especially in gymnastics, diving, and weightlifting.
- Monitoring young athletes: persistent low back pain > 2 weeks in an adolescent athlete always warrants further investigation.
Frequently Asked Questions (FAQ)
It depends on the stage. Acute stress fractures (with bone edema) can heal completely with rest and bracing in 6-12 weeks. Chronic fractures and pseudoarthroses will likely not heal at the bone level, but this does not necessarily mean pain: muscle strengthening allows most patients to return to an active and athletic life without pain, even with an unconsolidated pars.
Yes, most athletes return to sport after an adequate rehabilitation program. Return generally occurs in 3-6 months. However, it is important to correct risk factors (technique, training volume) and maintain a core stabilization program. Consult your doctor or physical therapist for a personalized re-athleticization program.
Spondylolysis is the fracture/defect of the pars interarticularis. Spondylolisthesis is the forward slippage of one vertebra over the one below it, which can be a consequence of bilateral spondylolysis. Not all spondylolyses evolve into spondylolisthesis, and spondylolisthesis can also have causes other than spondylolysis (degenerative, dysplastic).
Not always. A brace is recommended especially in acute and active fractures (with bone edema on MRI or positive SPECT), to promote bone healing. In chronic spondylolysis or pseudoarthrosis, a brace is less meaningful because bone healing is not expected: treatment is based on muscle rehabilitation. The decision should be made with the specialist doctor based on imaging.
No. Up to 50% of spondylolyses are completely asymptomatic. Many are discovered incidentally during X-rays performed for other reasons. The presence of spondylolysis on an X-ray in a patient with low back pain does not necessarily mean that spondylolysis is the cause of the pain: an accurate clinical evaluation is essential to establish the correlation.
There is a certain familial predisposition, but the risk is not high. If children practice sports involving hyperextension (gymnastics, diving, dance), it is useful to educate them about the importance of core strengthening and to monitor for any episodes of persistent low back pain. Preventive radiographic screenings are not necessary in the absence of symptoms.
Scientific References
- Lin LH et al.. Effectiveness of Lumbar Segmental Stabilization Exercises in Managing Disability and Pain Intensity Among Patients With Lumbar Spondylolysis and Spondylolisthesis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Spine (Phila Pa 1976) (2024). PubMed | DOI
- Lurie J, Tomkins-Lane C. Management of lumbar spinal stenosi (restringimento del canale vertebrale o vascolare)s. BMJ (2016). PubMed | DOI
- Brinjikji W et al.. MRI Findings of Disc Degeneration are More Prevalent in Adults with Low Back Pain than in Asymptomatic Controls: A Systematic Review and Meta-Analysis. AJNR Am J Neuroradiol (2015). PubMed | DOI
Frequently Asked Questions
What is spondylolysis?
Spondylolysis is a stress fracture or defect in the pars interarticularis, which is the portion of bone connecting the superior and inferior articular facets of a vertebra. It predominantly affects the fifth lumbar vertebra (L5) and is a common cause of low back pain, especially in young athletes.
What are the primary causes and risk factors for spondylolysis?
The primary cause of spondylolysis is repeated hyperextension of the lower back, which places significant stress on the vertebral pars interarticularis. This condition is particularly common in young athletes involved in sports that require repetitive spinal extension, such as gymnastics, diving, and weightlifting.
How is spondylolysis typically diagnosed?
Diagnosis of spondylolysis typically involves a clinical examination to assess symptoms and range of motion. Imaging studies, such as X-rays, MRI, or CT scans, are then utilized to confirm the presence and extent of the stress fracture in the pars interarticularis.
Can back pain from a cracked spine bone heal without surgery?
Conservative treatment for spondylolysis usually begins with a period of relative rest to facilitate healing of the stress fracture. This is followed by a structured program of physical therapy and strengthening exercises, guided by a physical therapist, to restore core stability and prepare for a gradual return to activity.
For a broader overview of related conditions, see our complete guide to back pain.
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Sources and Scientific References
- McNeely ML et al. (2003). A systematic review of physiotherapy for spondylolysis and spondylolisthesis. Man Ther. 8:80-91. DOI | PubMed
- Lurie J et al. (2016). Management of lumbar spinal stenosis. BMJ. 352:h6234. DOI | PubMed
- Lin LH et al. (2024). Effectiveness of Lumbar Segmental Stabilization Exercises in Managing Disability and Pain Intensity Among Patients With Lumbar Spondylolysis and Spondylolisthesis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Spine (Phila Pa 1976). 49:1512-1520. DOI | PubMed
- Kalichman L et al. (2008). Diagnosis and conservative management of degenerative lumbar spondylolisthesis. Eur Spine J. 17:327-335. DOI | PubMed
- García-Ramos CL et al. (2020). Degenerative spondylolisthesis I: general principles. Acta Ortop Mex. 34:324-328. PubMed