The question everyone asks (and the answer nobody likes)

Runners are a particular breed. I've been treating them for over two decades now, and there's a predictable conversation that happens in almost every first appointment. It goes something like this:

"I've had this pain for a while. I tried resting it. It got better. I ran again. It came back. So... should I just push through?"

The honest answer is: it depends on what's actually going on. Which I know isn't satisfying. But let me break it down in a way that actually helps you make a sensible decision, rather than just guessing.

Not all knee pain is the same

This is where most running advice falls flat, because it treats the knee as one thing. It isn't. There's the front of the knee, the back, the inside, the outside, and all of them can be grumpy for completely different reasons.

Patellofemoral pain (the achy, diffuse soreness around the kneecap that tends to build gradually) often responds differently to load than, say, a meniscal issue or iliotibial band syndrome. Treating them all the same way is a bit like treating a sprained ankle and a stress fracture with the same protocol because they both hurt when you walk.

So the first thing I'd always say is: know your diagnosis. If you're still in the "I think it might be..." stage, that's worth sorting out before you make any decisions about training.

The traffic light rule I use in clinic

When someone comes in asking whether they can run, I use a simple three-category system. It's not perfect, but it gives people a useful framework when they're trying to make a sensible call on a Tuesday morning before a training run.

Green: Run (with awareness)

Mild discomfort that's a 1 or 2 out of 10. It warms up within the first five to ten minutes and doesn't get worse as you continue. There's no swelling. No sharp or catching pain. No change to your normal gait pattern.

This kind of discomfort is often stiffness or low-grade irritation, and in many cases, a gentle run can actually be part of the recovery process rather than a setback.

Amber: Modify before you run

Pain that's a 3 or 4 out of 10. It might warm up, but it's inconsistent. You've noticed swelling at some point, even if not today. You're changing how you run to avoid it, even slightly.

This is the "proceed with caution" zone. It doesn't mean stop entirely, but it does mean shorter distances, reduced intensity, and paying proper attention to what the knee is telling you rather than drowning it out with a playlist.

Red: Stop and get it assessed

Pain above a 5. Sharp, catching, or locking sensations. Swelling that doesn't settle overnight. Pain that's getting progressively worse over several runs rather than staying the same.

If this is you, continuing to run is not being tough or disciplined. It's just making the overall problem worse and extending the time before you're fully back on the road.

The bit most people skip: why the pain is there

Here's something worth sitting with. Knee pain in runners is almost never a knee problem. It's a loading problem, a technique problem, or a combination of both.

The knee is, biomechanically, a fairly simple hinge joint. It bends and straightens. That's largely what it does. When it starts hurting, it's usually because it's being asked to manage forces it isn't well-positioned to handle, often because of what's happening at the hip above it or the ankle and foot below it.

I see it constantly. Weak hip abductors causing the knee to dive inward on loading. Stiff ankles causing compensatory movement further up the chain. Poor foot strike patterns adding excessive impact through every single stride. Over a week of running, those repetitive forces add up to a lot of stress on tissues that weren't designed to manage it alone.

This is why the question "should I run through it?" is often less important than "why is it happening in the first place?" The pain is a signal. It's worth listening to rather than negotiating with.

A word on rest, because it's more complicated than it sounds

Rest is not always the answer. I want to be clear about that, because a lot of people hear "get it checked out" and assume they're about to be told to sit on the sofa for six weeks.

The research on this has shifted significantly in recent years. We know that complete rest can lead to deconditioning, that tendons in particular respond better to graduated load than to total unloading, and that in many cases, the right kind of movement is genuinely therapeutic rather than harmful.

What we're looking for is not rest in the passive sense. It's relative rest: reducing the activities that are aggravating the tissue while maintaining movement, strength work, and cardiovascular fitness through alternatives like cycling or swimming if needed. The goal is to keep you as an athlete throughout the recovery process, not to put you on the shelf.

Lastly a point on what running in pain does

There's another reason to take knee pain seriously that most people aren't aware of, and it changes the conversation completely.

Within about 36 hours of experiencing pain during movement, your brain starts quietly reorganising things. It begins rerouting how you move to avoid triggering the painful pattern. You probably won't even notice it happening. Your stride might shift fractionally, your hip might hike slightly, your foot might land a little differently. It feels fine. You're still running. Problem solved, right? Not quite.

By around 72 hours, if the pain is still present, the brain starts to make that compensation more permanent. It essentially disconnects the motor engram, which is the neurological programme that drives the original movement pattern, and replaces it with the workaround. At that point, you're no longer just dealing with a sore knee. You're running on a rewritten movement programme that's loading your body asymmetrically, placing stress somewhere it was never designed to absorb, and doing so consistently, with every single stride.

This is how a knee problem becomes a hip problem three months later. Or why a runner comes to me with a calf injury and we trace it back to a foot issue they'd "sorted themselves" earlier in the year. The original pain went away. The compensation stayed.

The good news is that these patterns can be identified and corrected. But it's considerably easier to do that early, before the nervous system has had time to bed them in. The longer you wait, the more unpicking there is to do.

What I'd actually recommend

If your knee has been bothering you for more than two or three weeks, or if you keep having the same problem flare up every time you increase mileage, don't keep trying to guess your way through it. I know it feels like a big step to book an appointment, but an assessment takes an hour, gives you an actual diagnosis, and usually produces a clear plan for getting back to full training.

Most of the runners I see wish they'd come in sooner. Not because the problem was serious, but because they spent months running cautiously and inconsistently when a few targeted sessions would have sorted it out much earlier.

The knee you're working around isn't the enemy. It's just trying to tell you something. The sooner you find out what that is, the sooner you're back to running freely.