When I talk about a structural problem, I mean something about the physical build of the knee that means the kneecap was never going to track properly — regardless of how strong the surrounding muscles are.

This is the part people find hard to accept, and understandably so. You can have strong glutes, excellent VMO activation and perfect foot control, and still have a kneecap that tracks badly. Not because you haven’t worked hard enough, but because the problem simply isn’t in the muscle. No amount of strengthening fixes a problem that lives in the bone and the geometry of the joint.

There are two main structural issues I see driving this, and once you understand them, everything starts to make sense. The first is patella alta, and the second is an increased TT-TG distance. Let me explain both in plain terms, because they’re the key to understanding why your runner’s knee won’t go away.

There are two main structural issues I see driving this, and once you understand them, everything starts to make sense. The first is patella alta, and the second is an increased TT-TG distance. Let me explain both in plain terms, because they’re the key to understanding why your runner’s knee won’t go away.

Patella alta simply means the kneecap sits too high.

In a normal knee, when you bend and straighten, the kneecap sits within a groove at the bottom of the thigh bone called the trochlear groove. That groove is what keeps the kneecap stable and guides it as it moves — think of it like a train running along a track. As long as the train is on the track, it goes exactly where it should.

The important detail is that the groove only really starts to engage and control the kneecap once the knee is bent to a certain angle. If the kneecap sits too high, it spends much of its time sitting above the groove rather than down in it — in other words, off the track.

So every time you load that knee — going downstairs, squatting, getting up out of a chair — the kneecap is moving without the bony stability of the groove guiding it. It’s relying entirely on the soft tissue and muscles around it to stay centred, and that’s a losing battle in the long term, no matter how well conditioned those muscles are.

The higher the kneecap sits, the less time it spends in the groove, and the more unstable and irritable it becomes under load. That’s why, for someone with patella alta, the pain keeps returning even after they’ve done all the right rehab.

The second structural issue is the TT-TG distance, and this one is really important to understand.

TT stands for tibial tubercle — that’s the bony bump just below your kneecap on the shin, where the patellar tendon attaches. TG stands for trochlear groove — the groove on the thigh bone where the kneecap sits.

In a normal knee, these two landmarks line up reasonably well. The attachment point of the kneecap tendon on the shin sits roughly in line with the groove the kneecap runs in on the thigh. So when the quad contracts and pulls through the tendon, it pulls the kneecap straight up the groove — cleanly and efficiently, with no sideways drift.

But when the tibial tubercle sits too far to the outside, the TT-TG distance becomes too wide, and the angle of pull changes. Now, every time the quad fires, it isn’t pulling the kneecap straight up the groove — it’s pulling it outward as well as upward. The kneecap is being dragged sideways with every contraction, every step, every single stride.

The measurement that matters here is around 12 millimetres. Within that, the TT-TG distance is generally considered normal. Once it goes beyond that — and particularly once it’s significantly beyond it — it becomes a real problem. The wider the distance, the greater the sideways pull on the kneecap, and the more pain and instability you get under load.

And here’s the crucial point: no exercise changes that measurement. You cannot strengthen your way out of a geometry problem. The angle is the angle, and until it’s properly addressed, the kneecap will keep being pulled off track — which is exactly why this kind of runner’s knee won’t go away with rehab alone.

The reason all this gets missed so often is that it doesn’t show up without the right imaging. You can’t feel it on examination, you can’t see it on a standard X-ray, and it won’t get picked up unless someone is specifically looking for it. That’s why so many people spend months or even years going through rehab, doing everything right, getting temporary relief and then watching the pain come straight back — with nobody ever measuring their TT-TG distance or checking the height of their kneecap.

I see this regularly in clinic: people who’ve been round the houses with their knee pain and never had a real answer, and when the right investigations are finally done, the cause shows up as clear as day.

So if you’ve been through proper physio, done the right exercises consistently, and the pain keeps returning, this is the conversation that needs to happen. You need imaging — specifically an X-ray to assess the height of the kneecap, and an MRI to measure the TT-TG distance and show what’s happening inside the joint. That measurement has to be looked at deliberately; it isn’t something that gets flagged by accident.

You also need the right person looking at it. That means an experienced knee consultant who specialises in patellofemoral problems — not a GP, and not a general assessment. It needs specialist eyes. If the measurements come back significant, whether that’s a kneecap sitting too high or a TT-TG distance beyond where it should be, there are surgical options that can correct the underlying mechanics. But that’s a discussion to have with the right consultant, with the right imaging in front of them.

The takeaway is simple. If you’ve done everything right and the kneecap pain on those stairs still isn’t shifting, don’t keep going round in circles. Ask for the right investigations and get in front of an experienced knee specialist — because sometimes the problem is structural, and once that’s identified, there’s finally a clear path forward.

Joe Sharp
BSc (Hons) Physiotherapy