Why does my back hurt at my desk?

Search this exact question and the internet will hand you a diagnosis inside of a sentence. A muscle, a disc, a posture with a scary name. We are not going to do that, because we are not qualified to and it would not be honest.

What we can do is narrow the question to the part that is actually ours to talk about: the equipment. A desk, a chair and a monitor have a geometry— a set of heights and angles and distances — and that geometry is adjustable. Occupational safety bodies publish what a neutral version of it looks like. So instead of guessing at why your back hurts, this page walks the four things about that geometry you can change, describes each one against a published figure, and stops precisely where the geometry stops. Whether any of it relates to what you are feeling is not a question a spec sheet can answer.

The four levers, in the order we will take them: where your feet end up, what your lower back is touching, how far below your eyes the screen sits, and how long you hold any of it still.

What this page is not

This is not medical advice, and it is not written by anyone qualified to give any. Stephen is a home-office enthusiast who reads standards documents and manufacturers’ spec sheets. He is not a physiotherapist, an ergonomist, or a clinician, and he has not examined you, your back, or your desk. What follows describes equipment geometry and quotes what OSHA, Cornell and a Cochrane review have published about seated posture. It does not diagnose a cause, and it does not promise that any change will reduce, prevent or cure anything you feel. Those are the two things it deliberately refuses to do.

If your back hurts consistently, the person to talk to has a license and can put hands on the problem. A page ranking footrests cannot. Read the geometry below as a checklist of what is adjustable, not as an explanation of a symptom.

Lever one: where the chair leaves your feet

Start at the floor, because everything above it is stacked on this. OSHA’s Good Working Positions guidance describes a neutral seated posture as, among other things, feet flat on the floor or supported by a footrest, with the thighs roughly parallel to the floor. That is a geometry, and it is one most people quietly break for a reason that has nothing to do with their legs: they raise the seat to reach a desk that is too tall.

Here is the trap. A fixed desk is usually around 29″, and that height was not chosen to fit you. If the desk is too high, the intuitive fix is to wind the chair up until your forearms reach the surface — and the moment you do that, your feet leave the floor. Now the front edge of the seat is carrying the weight of your dangling legs, and the parallel-thigh geometry OSHA describes is gone. The desk problem became a leg problem one turn of the gas lift ago.

OSHA does not give a magic seat-height number, and neither will we, because the right height depends on your legs and your desk at once — its chair page offers a “fit test” instead. The two ways back to the geometry are to lower the working surface toward you, or, if the desk will not move, to give your feet a floor at the new height. That second one is what a footrest is: the floor the raised seat took away. The order to set the seat, the desk and your feet in is laid out on how to adjust your chair. And while you are down there, OSHA’s desk page is worth a glance for the clearance underneath — thigh, knee and toe room — because a drawer or a crossbar where your knees want to be forces its own compromise.

Lever two: the gap behind your lower back

Sit all the way back in your chair and notice whether your lower back is touching anything. For a great many desk workers the honest answer is no — they perch on the front third of the seat, lean toward the screen, and the backrest is a thing behind them rather than under them.

OSHA’s chair page describes the geometry the other way around: the backrest should support the curve of the lower back, and it should be able to recline to roughly 15 degrees rather than sit bolt upright. Both of those depend entirely on contact. A backrest supports nothing you are not leaning against, and a recline you never use is a hinge that has never moved. The gap between the small of your back and the seatback is the whole story of this lever, and it is the one people miss because it is behind them.

This is where lumbar support belongs in the picture — and where it is routinely oversold. Lumbar support is the part of the backrest, or the cushion added to it, that fills the hollow of your lower back so the curve has something to rest against. It does that job only when you are sitting back against it; parked forward on the seat, the most elaborate lumbar mechanism in the world is touching air. What the feature is, what it is not, and when a built-in one beats a strapped-on cushion is the whole of what lumbar support actually does. We are describing where the backrest sits relative to your spine. We are not telling you a cushion treats a symptom — that is not a claim a chair page gets to make.

Lever three: a screen low enough to fold you forward

Now look up, because the screen quietly governs the two levers below it. OSHA writes the target plainly on its monitors page: “the top of the monitor should be at or slightly below eye level”, with the center of the screen “15 to 20 degrees below horizontal eye level” and the panel “between 20 and 40 inches” from your eyes. A laptop on the desk, or an external monitor sitting on its factory stand, is very often well below that line.

The geometry of a low screen is easy to describe and easy to feel. Your eyes go to the middle of the screen; if the middle is low, the head tips down to meet it; and because the head is heavy and cantilevered on the neck, the upper back rounds forward to follow. What began as a screen a few inches too low becomes a whole torso folded toward the desk. That is a description of posture — head, neck and upper back in a forward curve — and it is geometry we can point at. It is emphatically not a claim about what is happening inside your back, which we have no way to know.

The fix is dull and mechanical: bring the top of the screen up to your seated eye line so the head can balance over the spine rather than hang in front of it, which is the other half of OSHA’s Good Working Positions description — the head balanced over the spine. How to find that eye line, and whether a stack of books, a stand or an arm is the right way to reach it, is the whole of the monitor height guide. The one caution: raise the screen and the laptop keyboard goes up with it, so a laptop needs an external keyboard the same day — solving the neck geometry is not worth trading for a wrist one.

Lever four: one position, held too long

The fourth lever is the one that survives getting the other three perfect, because it is not about any single setting. It is about holding any setting for hours without moving.

There is a common misreading of the first three sections worth heading off here: that the goal is to find the One Correct Posture and then freeze in it for eight hours. The sources point the opposite way. Cornell’s ergonomics guidance on sit-stand work is to changeposture regularly — to move between positions rather than hold one rigidly, standing stiffly included. A perfectly neutral posture held motionless all day is still one position held all day.

This is also the honest context for the standing-desk conversation, and it is worth being careful about what the evidence actually says. The Cochrane review of sit-stand desks (CD010912) found they cut sitting time — by roughly 100 minutes a day in the short term, tapering to about 57 minutes at medium-term follow-up — but it rated that evidence low quality and described broader health benefits as unproven. Notably, it also reported no harms. So the defensible reading is narrow: the value in a sit-stand setup is that it makes changing position easy, not that standing is a treatment for anything. Standing rigidly for eight hours would just be a new single position. What that evidence supports, and what it does not, is the whole of standing desk vs sitting.

The free version of this lever needs no purchase at all: get up, change what you are doing with your body, and come back. A desk that raises costs money and makes the change easier; a timer and a glass of water on the far side of the room costs nothing and does the same job less conveniently.

The order to change them in

If you are going to touch all four, the sequence matters, because each one moves the reference point for the next. Set them from the floor up, the way the ergonomic desk setup lays it out.

First the seat, against your feet and thighs — get feet flat and thighs roughly level before anything else, because this is the datum everything above it is measured from. Then the backrest, so your lower back is actually in contact with it rather than leaning away toward the desk. Then the desk surface relative to your forearms, adding a footrest if reaching the surface lifted your feet. Only then the screen, raised to the eye line you now sit at — because if you set the monitor first and then change your seat height, you have to set the monitor again. And running underneath all four, the reminder that none of these is meant to be held frozen: the best-set desk in the world still wants you to get up and move.

Do it in that order and each adjustment holds. Do it in any other order and you will chase your own settings around the desk, which is its own small source of the frustration that sent you searching in the first place.

What we can and cannot tell you

We can tell you what a neutral seated geometry looks like on paper, because occupational safety bodies publish it and we have quoted them and linked them: feet supported, thighs level, lower back in contact with a reclining backrest, the top of the screen at or just below eye level, and no single position held for hours. Those are describable, checkable, adjustable things, and the four of them are genuinely within your control at your own desk.

What we cannot tell you is whether any of them is the reason your back hurts, or whether changing them will make it stop. That is not modesty — it is the line between describing equipment and practising medicine, and we are on the equipment side of it by a wide margin. Stephen reads standards documents and spec sheets, not patients. If your back hurts consistently, take it to someone who can examine you and who has training we do not. Set the geometry because it is worth setting; see a clinician about the pain, because that is what a clinician is for.