L4–5 facet joint arthropathy with foraminal stenosis

The lumbar spine is the lower part of your back. L4–5 is the level between the fourth and fifth lumbar bones.

Each level has two facet joints at the back. They guide movement and help steady the spine. Facet joint arthropathy means that a facet joint has arthritic change. The joint cartilage, bone and surrounding tissue can change over time. An arthritic facet seen on a scan is common and is not always painful.

A neural foramen is a side opening where a nerve leaves the spine. Foraminal stenosis means this opening is narrower than usual. At L4–5, foraminal narrowing may affect the exiting L4 nerve root.

This is different from narrowing in the lateral recess at L4–5, which more often affects the L5 nerve travelling past that level. This page is about foraminal, not lateral-recess or central-canal, stenosis.

Facet enlargement can add to narrowing of the nearby foramen. Changes in a disc, small bony growths, loss of disc height or vertebral slippage can also contribute. The facet joint is not always the only cause.

Possible facet-related symptoms

Facet-related pain is usually felt in the lower back. It may spread into the buttock or upper thigh. Some movements or long periods in one position may aggravate it, but no single symptom or examination test proves that a facet joint is the source.

Possible L4 nerve symptoms

Irritation or pressure on the L4 nerve may cause pain, tingling, numbness or altered feeling. One possible pattern runs through the front of the thigh, around the knee and down the inner part of the lower leg.

The L4 nerve also helps muscles that straighten the knee. Weakness may make stairs harder or cause the knee to give way. A clinician may find a change in strength, feeling or the knee reflex.

Real nerve symptoms often do not follow a neat textbook map. Symptoms outside this pattern do not automatically rule out L4 irritation, and symptoms in this area can have other causes.

Facet arthritis and foraminal narrowing are common scan findings, including in people without pain. A report may describe narrowing as mild, moderate or severe, but this does not measure how much pain or disability a person has.

The same scan appearance can affect people differently. Symptoms also change over time without a matching change on a scan. Your history and examination help decide whether the L4–5 findings are likely to matter for you.

You may not need another test if the diagnosis is clear, your symptoms are stable, there is no concerning weakness or other warning sign, and a new result would not change care.

When a test could change the next step, your clinician may consider:

• MRI to look more closely at the nerve, disc and other soft tissues, or to reassess new or worsening nerve symptoms;
• CT to show bone and the size of the foramen, especially when MRI cannot be used or a procedure is being planned;
• X-rays, sometimes while bending or standing, if movement, slippage or instability is a concern;
• nerve-conduction and muscle tests when the source of weakness or altered feeling is unclear; or
• blood tests when symptoms suggest infection, inflammation or another illness rather than routine arthritic change.

New or worsening weakness, bladder or bowel symptoms, saddle numbness, fever with severe back pain, major trauma, or another serious concern may require urgent assessment and imaging.

The right plan depends on your symptoms, examination, daily function, other health conditions and preferences. Treating a scan finding without a matching clinical problem is unlikely to help.

A shared foundation

• Learn what the scan does and does not show, and agree on which changes in symptoms should prompt review.
• Keep moving and continue usual activities as you can. Prolonged bed rest can reduce strength and confidence.
• Pace demanding tasks, change positions and build activity gradually rather than cycling between overdoing it and long rest.
• A physiotherapist or exercise physiologist can help tailor strength, movement and aerobic activity to your ability and goals. There is no single exercise program for everyone.
• Address sleep, work demands, mood and worry where they are affecting pain or recovery.
• Pain medicines may sometimes support activity for a short period. Options can include an anti-inflammatory medicine such as ibuprofen, or paracetamol in selected plans. Suitability and benefit vary, and medicines can cause harm. Check with your GP or pharmacist, especially if you have kidney, stomach, heart or liver problems, take blood-thinning medicine, are pregnant, or use other pain medicines.

When facet-related back pain seems to be the main problem

Rehabilitation and self-management remain the base of care. Your clinician may also reassess the hips, muscles, discs, sacroiliac joints, sleep and other factors that can contribute to back pain.

If localised back pain remains important despite suitable non-surgical care, a pain specialist may consider a diagnostic medial branch block. A small amount of local anaesthetic is placed near nerves that carry feeling from the facet joint. A clear, short-term response can help judge whether the facet joint is a likely pain source; it is not a perfect test.

For carefully selected people who have a positive diagnostic response, radiofrequency treatment may be considered. It uses heat to interrupt the small medial branch nerves. Relief is not guaranteed and may be temporary because nerves can recover.

These facet-directed procedures do not enlarge the foramen and are not intended to take pressure off the L4 nerve.

When L4 nerve symptoms seem to be the main problem

Your clinician may monitor pain, feeling, muscle strength, the knee reflex, walking, stairs, sleep and daily activities. Further imaging or review by a pain specialist, rehabilitation physician, spinal surgeon or neurosurgeon may be useful if it could change care.

A selected nerve-root or epidural injection may be considered for severe or persistent nerve pain. It places local anaesthetic, often with a corticosteroid, near the irritated nerve. It may reduce pain for a time and help rehabilitation, but it does not permanently widen the foramen. Benefit is not guaranteed, and the procedure has risks that should be discussed first.

Nerve-directed treatment does not necessarily treat pain coming from a facet joint.

When might surgery be discussed?

Surgical assessment may be reasonable when matching L4 nerve symptoms remain severe despite suitable non-surgical care, when function is substantially limited, or when weakness is significant or worsening.

The main purpose is nerve decompression: making more room in the narrowed exit to relieve pressure on the L4 nerve. This may be called a foraminal decompression or foraminotomy.

A spinal fusion is not automatic or routine. It may be considered in selected cases if there is instability, deformity, vertebral slippage, or if enough bone must be removed during decompression that the level could become unstable. A surgeon can explain the expected benefit, limits and risks for the particular anatomy.

Symptoms can settle, flare or change. Scan changes and symptoms do not always progress together. The most useful signs of progress are often what you can do: walking, sleeping, working, climbing stairs and managing daily activities.

Arrange reassessment if symptoms keep limiting your life, the current plan is not helping, or your pattern changes. Increasing numbness, new weakness, repeated falls or a clear drop in function needs earlier review. Rapid weakness or bladder, bowel or saddle symptoms needs emergency assessment.

Back and leg symptoms often have more than one contributor. Muscles, discs, hips, sacroiliac joints, peripheral nerves, circulation, sleep, stress and other health conditions can affect the pattern and its impact.

Your clinician may review these possibilities if the symptoms do not fit an L4 pattern, the examination points elsewhere, or treatment aimed at one mechanism has not helped.

• Prolonged bed rest can lead to loss of strength and usually does not improve recovery.
• Repeat scans for unchanged symptoms are unlikely to help unless the result could change management.
• Spinal injections for non-specific back pain are not routinely recommended. A targeted procedure has a different purpose and needs careful selection.
• Gabapentinoids, oral corticosteroids, benzodiazepines and long-term opioid medicines for sciatica are not routinely recommended in major guidelines because overall benefit is limited and harms can occur. Do not stop a medicine suddenly; discuss a safe review with the prescriber.
• Fusion for back pain alone is not routine. This is different from selected cases where instability or the planned decompression creates a specific reason to consider fusion.

Not routinely recommended does not mean never used. Individual circumstances and specialist advice may change the balance.

• Facet joint: One of the small paired joints at the back of each spinal level.
• Arthropathy: A change or disease affecting a joint; here it means arthritic change in a facet joint.
• Neural foramen: A side opening between spinal bones where a nerve leaves the spine.
• Stenosis: Narrowing of a space.
• Nerve root: The first part of a nerve as it leaves the spine.
• Decompression: A procedure that creates more space around a nerve.