If you came in about your back and left having answered a dozen questions about your legs, there is a good reason. Here is what those questions are really for.
Have you seen a clinician about your back pain, only to find they seem far more interested in your legs? It is a common source of puzzlement, and occasionally of frustration. Let me explain what is going on, because those questions are doing a great deal of work.
What leg symptoms tell us
When a nerve is affected, by a slipped disc for instance, it produces symptoms in the leg.
In sciatica from a disc herniation, the herniated fragment pinches a nerve and sends pain along the distribution of that nerve, down the leg. Nerve compression also causes weakness and numbness in the leg.
This is why the questions are so detailed. A careful history covering exactly where the pain travels, combined with clinical examination, allows us to work out which specific nerve in the lumbar spine is compressed. An MRI scan then confirms it.
A different pattern: spinal stenosis
Nerve compression can also arise from stenosis, a narrowing of the central canal through which the nerves run. This usually results from wear and tear, with thickening of the ligaments and the joints connecting the bones, gradually narrowing the canal.
The pattern here is distinctive. Patients describe pain radiating down both legs on walking or standing for a period, which eases when they stop, sit down or lean forwards.
Notice that the story itself points to the diagnosis before any scan is taken. That is why the questions come first.
What surgery can and cannot do
Here is the heart of the matter.
Spinal surgery is effective at relieving leg pain. When leg symptoms are present, we can usually give you a reasonably good prediction of how effective an operation would be, though surgery is not necessarily the first-line treatment.
Back pain, with some exceptions, cannot really be treated surgically. Multiple structures in your spine may be contributing: discs, joints, muscles and ligaments. Isolating one and being confident it is the source is genuinely difficult.
Compounding this, many of the findings we see on MRI — wear and tear, worn discs, worn facet joints — are very common in people with no back pain at all.
The symptom we take most seriously
Leg weakness concerns us more than almost anything else, because it signals that the nerves supplying the legs are beginning to lose function.
Our job as surgeons is to preserve that function, and to reverse it where possible.
Sometimes the solution is straightforward: a disc fragment pinching a nerve, removed with a microdiscectomy, relieving the pain, with function typically returning over time. Higher up the spine, the spinal cord itself may be compressed, by a tumour for instance. There, the sooner we decompress it, the better your chances of recovering lost function.
This does not mean back pain doesn’t matter
I want to be clear about that. It is simply that identifying a single structure and being confident it is responsible is hard, for the reasons above.
But there are exceptions where we can be confident. A fracture, for example. Or a spondylolisthesis, where one bone has slipped forward over another. Depending on the history, examination and further tests, we are often sure this is the pain generator, and surgery to fuse the segment can be successful.
A term I dislike
I have little time for the phrase “non-specific lower back pain.”
We may not find a single identifiable structural cause on your scan. But dig deeper and there are mechanisms to be found. As a surgeon I can then direct a good physiotherapist or osteopath in managing the condition without an operation.
“Non-specific” too often sounds to patients like “we have nothing for you,” which is rarely true.
The key takeaway
Taking a detailed history with close attention to your leg symptoms is how we exclude anything serious that might need surgery.
So if your clinician spends what feels like a disproportionate amount of time on your legs, they are not ignoring your back. They are working out whether your back problem is one an operation can help.
