Why do I have lower back pain? The most common causes explained

Lower back pain is rarely random. There’s almost always a specific reason behind it — and working out which one matters, because effective treatment depends on understanding the cause.

Key takeaways

• Mechanical dysfunction — problems with how joints, muscles, and discs move — causes around 90% of lower back pain.
• Disc-related pain often builds with sitting and eases with movement; facet joint pain tends to be sharper and provoked by specific movements.
• Sciatica describes nerve pain travelling into the leg and is always caused by something — usually disc pressure or joint irritation at the nerve root.
• Poor posture and sedentary habits are a leading driver of lower back pain in people who spend a lot of time at a desk.
• Most lower back pain responds well to chiropractic care once the cause is properly identified.

What causes lower back pain?

Lower back pain is most commonly caused by mechanical problems — the way the spine’s joints, discs, and surrounding muscles are loading and moving. This broad category includes facet joint dysfunction, disc irritation, sacroiliac joint problems and muscular strain. Non-mechanical causes like inflammatory arthritis or referred pain from other organs make up a much smaller proportion of cases. For a full breakdown of multiple causes, our back pain diagnosis and causes guide covers the complete picture including red flag symptoms to watch for.

The most common causes of lower back pain

Muscle strains and ligament sprains

A muscle strain is one of the most straightforward causes of lower back pain. An awkward movement, heavy lift, or sudden twist can overstretch the soft tissues, causing immediate localised pain that’s tender to touch. It usually settles within a few weeks with appropriate movement and care — but if it keeps recurring, something underlying is driving it.

Facet joint dysfunction

The small joints at the back of each vertebra (facet joints) are a very common source of lower back pain. When these joints become restricted or inflamed, they produce a sharp, often one-sided pain that gets worse with specific movements — particularly extension and rotation. It’s the kind of pain that catches you when you turn over in bed or reach to one side.

Disc problems

A disc bulge or herniation can cause deep, aching lower back pain that builds with prolonged sitting and eases when you get up and move. When the disc presses on a nerve root, it can also cause pain, tingling, or weakness radiating down into the leg — this is sciatica. Disc degeneration (the gradual wear of disc material with age) is also a common contributor to chronic lower back pain.

Sacroiliac joint dysfunction

The sacroiliac joint sits where the base of the spine meets the pelvis. It’s a surprisingly common and commonly overlooked source of lower back and buttock pain. SI joint pain is often confused with disc-related sciatica because it can refer into the leg — but the distribution is usually different and a good orthopaedic examination can distinguish the two. SI joint pain can also be confused with hip pain – we often notice in clinic that patients describing their hip pain will point to their SI joint. Again, a good history and physical examination will distinguish the cause.

Poor posture and desk-related loading

Spending long hours sitting — particularly with a rounded lumbar spine and a forward head — places the lower back under sustained load that the spine was never designed for. Over time, this changes the position of the vertebrae and normal curves in the spine, creating the conditions for pain. If you recognise this pattern, our post on poor posture and back pain is worth a read.

Arthritis and age-related changes

Osteoarthritis in the lumbar spine — sometimes called spondylosis — is a gradual wearing of the facet joints and discs that becomes more common from the 50s onwards. It doesn’t always cause pain, but when it does the pattern is typically stiffness and achiness worse in the morning and after inactivity. We help people manage arthritis-related back pain regularly at Zest Chiropractic. If you’re unsure what’s behind your pain, an initial consultation with us is a good starting point. A thorough examination usually gives you a clear answer within one appointment. And if you’re really not sure, you can call us for advice. We’re always happy to talk to you to help you determine whether or not chiropractic care may be helpful for your back pain.

What type of lower back pain do you have?

Pain type	Likely cause	Key feature
Sharp, catches on movement	Facet joint	Worse rotating or extending
Deep ache, builds with sitting	Disc irritation	Eases with walking and movement
Pain into buttock or leg	Nerve root / sciatica	Burning, shooting, or electric
Lower back and buttock ache	Sacroiliac joint	Worse standing or climbing stairs
Morning stiffness, eases through day	Arthritis or inflammation	Pattern present for months or years

When should I see someone for lower back pain?

You should seek help when pain has lasted more than two to three weeks without improving, is getting progressively worse, is stopping you from working or sleeping, or is accompanied by leg symptoms. Certain symptoms — loss of bladder or bowel control, numbness in the inner thigh or groin, or weakness in both legs — require same-day emergency medical attention. For more on this, see our guide to when to see a chiropractor. Or, if you know you’re ready to get assessed, you can book an appointment here.