What Is Regional Interdependence — And How Does It Relate to Your Back Pain?

A patient comes in with low back pain. I check their hip range of motion. Almost every time, someone asks the same reasonable question: "why are you looking at my hip? My back is what hurts." It's a good question, and the honest answer is a real, formally described model in physiotherapy called regional interdependence.

What regional interdependence actually is

The term was formalised in 2007 by Wainner and colleagues in the Journal of Orthopaedic & Sports Physical Therapy, who defined it as the concept that "seemingly unrelated impairments in a remote anatomical region may contribute to, or be associated with, the patient's primary complaint."¹ In 2013, Sueki, Cleland and Wainner expanded it into a broader model — not just joints and muscles talking to each other mechanically, but a genuinely interconnected system worth examining as a whole rather than one sore segment in isolation.²

In plain terms: your back doesn't work in isolation. It sits between your hips and your ribcage, and how those regions move — or don't — changes the load your lumbar spine has to absorb. A proper back assessment looks at the whole chain, not just the part that hurts.

The best-evidenced example: your hip

Of all the regions studied alongside the low back, the hip has the most consistent evidence behind it. A study of professional golfers found that low back pain was associated with reduced hip and lower-back range of motion together, not the back alone.³ A separate study comparing active adults with chronic low back pain against pain-free controls found a genuinely large difference in passive hip extension — roughly 11 degrees less on average in the group with back pain, with no equivalent difference in hip rotation.⁴ That's specific: it's not "hips matter generally," it's a particular movement, in a particular direction, showing up again and again in people with back pain.

The logic isn't hard to follow. If your hip can't extend properly — the movement your leg makes swinging behind you when you walk, or straightening up from a forward bend — something else has to make up that range. Almost always, it's your lumbar spine picking up the slack, moving into more extension than it's really designed to on every stride and every bend, day after day.

That matters specifically because of where the load lands. The lumbar spine's facet joints — the small paired joints at the back of each vertebra — are built to bear weight during extension and rotation. Ask them to do that job more often than they should, because the hip upstream isn't contributing its share, and you have a direct, mechanical route to facet-mediated back pain: the kind that's often worse with standing, walking, or arching backward, and eased by bending forward. Restricted hip extension doesn't just correlate with back pain in the research — it gives you a specific, testable reason for a specific pattern of symptoms.

How we actually screen for this: the SFMA

Knowing that remote regions matter is one thing. Having a structured way to actually find which ones matter for a given person is another. That's what the Selective Functional Movement Assessment (SFMA) gives us — a movement-screening framework developed by Gray Cook and colleagues that runs a person through a set of full-body movement patterns, rather than jumping straight to the sore segment.

In practice, this is regional interdependence turned into a repeatable clinical process.

Hamstring flexibility is another region the SFMA routinely flags, and it's backed by the same kind of evidence as the hip: a 2017 systematic review that specifically pooled prospective studies — people measured before any back pain existed, then followed over time — found reduced hamstring flexibility predicted who went on to develop low back pain.⁵ The mechanism is straightforward: shorter hamstrings limit how far the hip can flex, so bending forward has to borrow that missing range from somewhere — and the lumbar spine is what's left to give it up. Over years of doing that on every forward bend, the spine is carrying more repetitive flexion load than it was built for, which is a credible driver of flexion-type back injuries, disc-related pain among them.

Worth being precise about what "tight hamstrings" actually means here, though. As I've written about separately, a muscle that feels tight usually hasn't physically shortened — more often it's the nervous system holding it under more tone than usual. Therefore, it is not simply enough to say "you have tight hamstrings, we need to stretch them." We need to determine the cause of that tightness and provide proper rehabilitation to allow the hamstrings to genuinely let go. Looser hamstrings, achieved that way, are what actually take the pressure off the lumbar spine — not a stretch held for thirty seconds before every session.

The bigger pattern: mobility and stability, stacked

The examples above are part of a bigger pattern — one that has been extensively researched and termed the "Joint-by-Joint Approach," developed by physical therapist Gray Cook — the same Gray Cook behind the SFMA — together with strength coach Mike Boyle.⁶ The idea is straightforward: each major joint in the body has a primary job, and that job alternates as you move up the chain. Some joints are built mainly for mobility — freedom to move through a large range. The joints next to them are built mainly for stability — resisting unwanted movement and controlling load. Working from the ground up, the pattern runs: foot (stability), ankle (mobility), knee (stability), hip (mobility), lumbar spine (stability), thoracic spine (mobility), scapula (stability), shoulder (mobility).

Reading bottom to top: the pattern alternates almost perfectly, right up the chain.

The knee is a good example of what "built for stability" actually means. Unlike the hip or ankle, it's not designed to rotate or move through much range beyond bending and straightening — it's meant to track cleanly under load while the joints above and below it do most of the moving. That's exactly why a stiff hip is such a common finding behind knee pain. If the hip won't rotate or extend the way it should, the knee is the next joint in line, and it starts absorbing movement — usually rotation, or the knee drifting inward under load — that it was never built to control. Long-term poor mechanics like this doesn't tend to cause an acute ligament injury; it's a more credible driver of a degenerative meniscal tear built up over years of the knee absorbing rotational load it wasn't designed for, and it's part of why we screen glute and hip function as closely as we do when someone's actual complaint is their knee.

The same logic runs the rest of the chain. A stiff ankle — commonly a restriction in dorsiflexion, the movement of the shin travelling forward over the foot — pushes extra rotation and instability up into the knee, which is the classic finding behind knees caving inward at the bottom of a squat. Further up, a stiff thoracic spine (the mid-back, which is naturally built for mobility but stiffens easily from long periods sitting) pushes the job of reaching overhead onto the lumbar spine below it or the shoulder above it — neither of which is designed to supply that range on demand, and both of which are common sites of the resulting pain.

What this means when you come in with back pain

It's part of why a thorough initial assessment for back pain takes longer than checking the sore segment and calling it done. We're looking at hip extension range specifically, hamstring length, and how your lumbar spine actually moves under load — not because it's thorough for its own sake, but because each of those has a real, published, sometimes predictive relationship with back pain outcomes.

In practice, that means an SFMA-based screen of the joints above and below your lumbar spine — hip extension and rotation, thoracic mobility, and how well your hips and glutes are actually controlling load rather than just how far they move. If the hip is genuinely restricted, we treat the hip, not just the back that's compensating for it. If a muscle comes back "tight," we're asking why the nervous system has turned that tone up before we ever reach for a stretch — because if it's a protective response to something else in the chain, stretching it is treating the alarm, not the fire.

It's also, incidentally, the same reasoning behind why we screen glute function as part of assessing lower limb and hip mechanics more broadly — the hip doesn't just extend on its own; the muscles controlling it matter just as much as the raw range of motion. And it doesn't stop at the hip. The same logic that connects your hip to your back connects your ankle to your knee, and your thoracic spine to your shoulder — which is exactly why an assessment for back pain at Move often includes joints that, on paper, have nothing to do with your back.

The point of all of this isn't to make a simple problem complicated. It's the opposite: back pain that keeps returning despite treating the back directly is usually a sign that the back was never the actual problem — it was the joint that ran out of options first. Find the joint that's actually restricted, and the back pain built on top of it tends to resolve a great deal faster than another round of treatment aimed only at where it hurts.

Daniel Ryan

Senior Physiotherapist · Founder, Move Physiotherapy & Fitness

Masters of Physiotherapy, University of South Australia. Founded Move Physiotherapy in 2018. Provides match day services to sporting clubs across Perth, with a focus on evidence-based rehabilitation and objective return-to-sport testing.