An L5–S1 MRI report describes the last lumbar disc, between the 5th lumbar vertebra and the sacrum. “Protrusion” means a herniation with a broad base, “extrusion” a herniation that has pushed out further than its base, and “nerve root compression” contact between the disc and a nerve root. The changes in the report are not always what is causing the pain.
Below you will find a simple glossary of terms used in MRI reports, an explanation of why the image and the symptoms do not always match, and information on when to see a doctor urgently with your result.
In brief
- L5–S1 is the lowest lumbar disc – together with L4–L5, the most common site of a herniation.
- Disc bulges are also seen on MRI in people without pain: in about 30% of 20-year-olds and about 84% of 80-year-olds.
- Numbness in the groin area, problems passing urine or weakness in a leg need urgent assessment by a doctor.
- Treatment, including surgery, is decided by a doctor; the physiotherapist assesses movement and chooses exercises. A consultation costs 180 PLN.
- The clinic in Rydułtowy is open Mon–Fri 7:00–20:00, private visits, no referral needed.
Contents
What does the L5–S1 level mean in an MRI report?
The symbol L5–S1 refers to the segment between the fifth and last lumbar vertebra (L5) and the first segment of the sacrum (S1). This is where the intervertebral disc sits that carries heavy loads when you bend and lift. A herniation at this level most often irritates the S1 nerve root, which can cause pain spreading down the back of the leg as far as the foot.
The radiologist usually describes each level separately: L3–L4, L4–L5, L5–S1. For each one they give the condition of the disc, the spinal canal and the intervertebral foramina through which the nerves exit. If the pain travels down your leg, also read our post sciatica – what to do.
What do the most common terms in an MRI report mean?
Most reports use a handful of recurring terms. They concern the shape of the disc (bulging, protrusion, extrusion, sequestration), its “ageing” (dehydration, loss of height), the condition of the bone (Modic changes, osteophytes) and the space available for the nerves (nerve root compression, narrowing of the canal or foramen). The glossary below explains them in plain language, without judging whether a given change is dangerous.
| Term in the report | What it means in practice |
|---|---|
| Bulging | the disc “sticks out” evenly over a large part of its circumference; common with age |
| Protrusion | a herniation with a broad base – the displaced fragment is narrower than the base |
| Extrusion | a herniation in which the displaced fragment is wider than its base |
| Sequestration | a fragment of the disc has broken off and lies free in the spinal canal |
| Disc desiccation (dehydration) | the disc contains less water and looks darker on the image – a typical sign of wear |
| Annular fissure | a tear in the outer layer of the disc |
| Nerve root compression | the disc touches, compresses or displaces a nerve root |
| Foraminal or canal narrowing (stenosis) | less space for the nerves, e.g. because of the disc, joints or ligaments |
| Modic changes (type 1, 2, 3) | changes in the bone right next to the disc, visible on MRI |
| Osteophytes | bony outgrowths on the edges of the vertebrae |
Terms such as “central”, “paracentral” and “foraminal” tell you in which direction the disc has moved. We write more about the condition itself in our post lumbar disc disease – does physiotherapy help.
Do the changes in an MRI report always explain the pain?
Not always. Bulges, protrusions and disc dehydration are often seen on MRI in people who feel no pain at all, and they become more common with age. That is why the report is always interpreted together with the symptoms and an examination. What matters most is whether the change matches the location of the pain, numbness or weakness, not what it is called.
In Brinjikji’s 2015 review of studies, disc degeneration was found in more than 1/3 of 20-year-olds without symptoms and in more than 90% of people over 80. The word “extrusion” sounds alarming, but on its own it does not determine treatment. On the other hand, a small change can cause clear symptoms if it irritates a nerve root. That is why the printout alone does not decide what happens next.
When should you see a doctor first?
Urgent medical help is needed for: numbness in the groin area or inner thighs, difficulty passing urine, urinary or faecal incontinence, rapidly increasing weakness in a leg or foot drop, pain after a fall or injury, fever with back pain, and severe night pain with unexplained weight loss. Such symptoms may require prompt diagnosis and treatment.
If you have problems passing urine or stools and numbness in the groin area, go to A&E (SOR) – these may indicate compression of the cauda equina. It is also worth going back to the doctor if the pain gets worse despite treatment.
Who should you see with your MRI report?
With your MRI report, go back first to the doctor who ordered the scan – they link the result with your symptoms and decide on treatment, including a possible neurosurgical consultation. The physiotherapist does not change these decisions, but assesses mobility, strength and how the pain responds to movement, and teaches safe exercises and positions. A consultation in Rydułtowy costs 180 PLN.
If you are not sure which specialist to start with, read our post back pain – who to see first.
Physiotherapy consultationassessment of movement and symptoms taking the MRI report into account, plan of exercises and habits180 PLNPrices valid from 08.2026. The physiotherapist decides on the number of visits individually after the consultation.
Good to know: bring the disc with the scan and the full MRI report to your visit, as well as any earlier results – comparing them helps to assess whether the changes have changed.
Summary
L5–S1 is the lowest lumbar disc, and “protrusion”, “extrusion” and “nerve root compression” describe the shape of the herniation and its contact with a nerve. Changes on MRI are often present without pain, so the result is always assessed together with the symptoms. Treatment is decided by a doctor, and numbness in the groin area or problems passing urine need urgent help.
Frequently asked questions
Is an L5–S1 protrusion the same as a herniation?
Yes, a protrusion is one type of disc herniation in which the displaced fragment is narrower than its base. It is sometimes called a smaller or “early” form of herniation, although the name itself does not tell you how severe the symptoms will be. What matters is whether the protrusion irritates a nerve root and whether it matches the patient’s symptoms.
Does a disc extrusion always need surgery?
No. Many patients with an extrusion are treated conservatively, and the decision about surgery is made by a doctor, most often a neurosurgeon or an orthopaedic surgeon. They mainly take the symptoms into account: increasing weakness, bladder or bowel problems, or severe pain that does not ease despite treatment. The MRI report alone, without examining the patient, does not decide on an operation.
Can a disc herniation get smaller?
Yes, a herniation can get smaller over time and may even be reabsorbed. Research suggests this applies especially to large extrusions and sequestrations, which the body more often “recognises” and gradually removes. However, it is impossible to predict whether and when this will happen in a particular person, so treatment decisions are always based on symptoms.
Can I exercise with an L5–S1 protrusion?
In most cases movement is advisable, but exercises have to be matched to the symptoms, not to the MRI report alone. First, a doctor should rule out situations that need urgent treatment. The physiotherapist checks which movements reduce and which increase pain or numbness, and on that basis puts together a safe set of exercises for home.
Sources
- Fardon D.F. et al., Lumbar disc nomenclature: version 2.0. Recommendations of the combined task forces of NASS, ASSR and ASNR, The Spine Journal, 2014.
- Brinjikji W. et al., Systematic literature review of imaging features of spinal degeneration in asymptomatic populations, American Journal of Neuroradiology, 2015.
- Chiu C.C. et al., The probability of spontaneous regression of lumbar herniated disc: a systematic review, Clinical Rehabilitation, 2015.
- National Institute for Health and Care Excellence (NICE), Low back pain and sciatica in over 16s: assessment and management (NG59), 2016, updated 2020.
About the author: Tatiana Grabowska, MSc – master’s degree in physiotherapy, licence to practise number PWZFz 11646 (Polish physiotherapist licence). Since 2013 she has run the “W zdrowym ciele” physiotherapy and rehabilitation clinic in Rydułtowy; she has about 12 years of professional experience.
- Consultation180 PLN
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