What is causing your lower back pain?

Lower back pain is one of the most common reasons people seek physiotherapy — and one of the most misunderstood. The term covers a wide range of conditions, each with a different cause, a different pattern of symptoms, and a different path to recovery.

The single most important thing to understand is this: where your pain is coming from determines how it should be treated. Treating muscle tightness the same way you treat a disc problem, or managing nerve pain the same way you manage a joint irritation, rarely works. A correct diagnosis is the foundation of effective treatment.

This article walks through the most common structural causes of lower back pain — what each one feels like, what makes it better or worse, and what physiotherapy does about it.

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The structures that cause lower back pain

Your lumbar spine — the lower portion of your back — is a complex structure made up of five vertebrae (bones), intervertebral discs, facet joints, ligaments, and the surrounding muscles. Pain can originate from any of these, and often from more than one at the same time.

1. Muscle and soft tissue strain

This is the most common cause of acute lower back pain. A sudden movement, heavy lift, awkward twist, or even a prolonged period of poor posture can overload the muscles and ligaments of the lumbar spine.

What it tends to feel like:

• Sharp or aching pain localised to the lower back, usually on one side
• Stiffness and tenderness when you press on the area
• Pain that worsens with movement and eases with rest
• No pain below the knee (the pain stays in the back and buttock)
• Onset linked to a specific activity or event

What makes it better: Gentle movement, warmth, keeping active within tolerance. Prolonged rest typically makes muscle-related back pain worse, not better.

What physiotherapy does: Manual therapy to reduce muscle guarding, soft tissue work to release tension, and movement rehabilitation to restore function and prevent recurrence.

2. Disc-related pain

Between each vertebra sits an intervertebral disc — a structure with a tough outer ring (annulus fibrosus) and a gel-like centre (nucleus pulposus). When the outer ring is stressed or torn, it can cause significant local pain. When the inner material pushes outward and presses on a nearby nerve root, it produces what most people recognise as sciatica.

What it tends to feel like:

• Deep, central or one-sided lower back pain, sometimes severe
• Pain that is worse sitting down than standing
• Difficulty finding a comfortable position
• If a nerve is involved: pain, tingling, or numbness that travels down one leg (often past the knee, into the calf or foot)
• Symptoms that are worse in the morning and ease slightly as the day goes on

What physiotherapy does: Directional movement therapy (often extension-based exercises), neural mobilisation to free the irritated nerve, and load management to allow the disc to recover without re-aggravation.

3. Facet joint pain

The facet joints are small paired joints at the back of each vertebra. They guide spinal movement and can become irritated through sustained poor posture, sudden overload, or gradual degeneration.

What it tends to feel like:

• Stiffness and pain after sitting or lying still for a period — particularly first thing in the morning
• Pain that eases once you get moving
• Aching in the lower back and sometimes into the buttock or back of the thigh (rarely below the knee)
• Difficulty straightening up or bending backwards
• Worsened by sustained extension (arching the back)

What physiotherapy does: Joint mobilisation to restore movement, postural correction to reduce sustained load on the joints, and targeted strengthening of the surrounding stabilising muscles.

4. Sacroiliac joint (SIJ) dysfunction

The sacroiliac joints sit at the base of the spine where it meets the pelvis. They are often overlooked as a source of back pain but account for a meaningful proportion of cases — particularly in people who have recently been pregnant, had a fall, or noticed pain that is very one-sided and close to the back of the pelvis.

What it tends to feel like:

• Pain in the lower back and upper buttock, typically one-sided
• A catching or locking sensation when turning in bed or getting in and out of a car
• Difficulty with single-leg activities — climbing stairs, standing on one leg
• Pain provoked by prolonged standing or walking

What physiotherapy does: Specific SIJ mobilisation, pelvic stability exercises, and load management for provocative activities.

5. Nerve root compression (sciatica)

Sciatica is not a diagnosis — it is a symptom. It describes pain that travels along the path of the sciatic nerve, from the lower back through the buttock and down the back of the leg. It is most commonly caused by a disc pressing on a nerve root, though other structures (including the piriformis muscle and the facet joints) can also irritate the nerve.

What it tends to feel like:

• A sharp, burning, or electric pain that travels from the back into the buttock and down the leg
• Numbness or pins and needles along the same path
• Symptoms below the knee, sometimes into the foot
• Coughing or sneezing may worsen the leg pain
• One leg typically affected, rarely both

What physiotherapy does: Identifying the root cause (disc, joint, or muscle), neural mobilisation to reduce nerve sensitivity, directional exercises specific to the pattern of symptoms, and activity pacing.

6. Postural and movement-related pain

This is increasingly common and often underdiagnosed. Sustained poor posture — particularly from desk work — places cumulative load on the passive structures of the lumbar spine. Over time, this creates low-grade irritation that builds into persistent pain.

What it tends to feel like:

• Gradual onset rather than a single event
• Aching that builds through the day, particularly after sustained sitting
• Relief on movement, worsening on return to sitting
• Stiffness across the whole lower back rather than a specific point

What physiotherapy does: Postural analysis and correction, workstation assessment, movement pattern retraining, and progressive strengthening of the core and hip stabilisers.

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When to seek urgent care

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Why the right diagnosis matters

Many people come to us after weeks of self-managing, trying exercises they found online, or following generic advice that has not helped. The reason it has not helped is usually straightforward: the treatment did not match the cause.

A thorough physiotherapy assessment — taking a detailed history, examining movement, testing reflexes and nerve function, and palpating the relevant structures — can identify which tissue is responsible for your pain with a high degree of accuracy. That diagnosis then shapes everything: which exercises, which manual therapy techniques, what to avoid, and what realistic recovery looks like.

Lower back pain, regardless of the cause, almost always responds to the right treatment. The question is finding the right one.