What causes left side back pain?

If you have left side back pain you may have non-specific lower back pain.  This is the most common type of back pain. Before I talk any more about left sided back pain you need to know that there are three main types or groups of back pain.(1)

  1. Non-specific - 95% of people with back pain have this type, it is by far the most common problem I see.

  2. Nerve root irritation- the layman's term for this is sciatica. It is caused by an inflamed or irritated nerve in your back. The pain can be confusing as it is most often felt in the buttock or leg. It's less common for it to be felt on the flank or sides.(True sciatica is actually not that common, less than 5% of people really have it. It seems more common because it is often misused to describe simple backache)

  3. Serious or specific back problems – these are worrying illnesses such as cancer and infection and fortunately very few people have this (less than 1%). These illnesses often have clear signs and symptoms, called red flags, and your doctor will know exactly what to look out for. You can see what some of them are by following the link at the bottom of the page. If you have any of the symptoms listed seek urgent advice from your doctor.


Non-Specific Lower Back Pain

left side back painThe term non-specific lower back pain is a term used to describe all of the non serious causes of back pain and can include all sorts of problems – several of them can cause left side back pain.

The problem with non-specific lower back pain is that it is exactly that – non-specific. This means that very often there is no obvious cause for the problem.

I have listed some possible culprits for acute left side back pain which may or may not apply to you:

Facet Joint Strain and Muscle Spasm

A common cause of acute lower left back pain is a facet joint strain and/or back muscle strain. Your spine is made up of large bones called vertebrae that are separated from one another by spinal discs. However, many people don’t realise that each vertebra overlaps the next and forms a pair of joints called facet joints. These joints enable movement in the spine, they are a bit like little finger joints.  If they become a bit sore or strained you may get protective muscle spasm which is where your muscles tighten up to try and protect the painful area, this can really hurt!

Fortunately this problem is not serious and managing it with pain relief and keeping active is usually enough to get the symptoms back under control.

Research Corner

An interesting research trial (2) compared anti-inflammatory tablets and/or spinal manipulation with simple advice to keep active in people with non specific acute back pain. The results showed no additional benefit from adding any treatment on top of keeping active.The Lancet's review (3) of current treatment advice also supports the need to self manage the problem with appropriate support from your doctor.

Sacroiliac Joint Pain

The sacroiliac joint is a very stable joint with very little movement but problems with the joint can occur if this movement becomes restricted or if there is too much movement in the joint. Too much movement sometimes happens after a fall or injury but most commonly after pregnancy. This is the main cause of back pain in pregnancy. This can cause right or left side back pain but is obviously a clear cause..

(Occasionally the joint becomes inflamed and this may be a sign of ankylosing spondylitis which is a type of arthritis and a specific problem, but aging this is very rare)

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Aging Changes

Changes occur in the joints as we age and can cause stiffness and pain in the facet joints of the lower back. This can cause right of left side back pain. Degenerative disc disease tends to cause central pain although pain can be referred outward to an area that is some distance away from the actual sore tissue. Changes in the discs can cause strain in the facet joints and can lead to the same muscle spasm that can be sore sore.

Referred Pain

Referred pain is pain that is felt away from the actual site of the problem.  An example is a gall bladder problem that can give you pain in your shoulder blade. The most well known example is a heart attack which may be felt as pain in the left arm.

Muscles and joints can refer pain in a similar way for example a facet joint strain can give you pain in the buttock. This can29-Jul-2017ly spot it.

Chronic versus Acute Pain

This whole thing is further complicated if you have chronic lower back pain, as the way your body responds to pain changes if you have had it for a while. If you have chronic pain bear in mind that it is very difficult indeed to pin point the exact cause of the problem.

Next Steps?

Without an assessment it is impossible to be sure of the exact cause of anyone’s pain, therefore I recommend that you go along to a doctor or physiotherapist and get checked out. This will do two things,

  • it will rule out any of the more serious causes of back pain and put your mind at rest,
  • you will also get specific advice for your problem.

It is highly likely that you will have a very manageable non specific lower back pain problem that you can treat with success.


1 .  Non-Specific or Simple Lower Back Pain Guidelines

2.Hancock, M.J. et al., 2007. Assessment of diclofenac or spinal manipulative therapy, or both, in addition to recommended first-line treatment for acute low back pain: a randomised controlled trial. The Lancet, 370(9599), pp.1638–1643.

3.Balagué, F. et al., 2012. Non-specific low back pain. Lancet, 379(9814), pp.482–491.


Lower Back Pain Toolkit Home Page

Back Pain Symptoms other than left side back pain

Serious problems and Red Flags