Hip Impingement (FAI): When the Hip Is the Real Story

A recurring theme in musculoskeletal care is that the spot that hurts is not always the source of the trouble. The hip is a classic example. Someone shows up with nagging knee pain, or a low back that tightens on one side, and the actual driver turns out to be a hip that cannot move cleanly into deep flexion. Femoroacetabular impingement, usually shortened to FAI syndrome, is one reason that happens, and it is worth understanding because it is frequently missed and frequently mislabelled.

What FAI syndrome actually is

The hip is a ball-and-socket joint. In FAI, there is a subtle mismatch in the shape of the ball, the socket, or both, so that at the end of certain movements the two make contact sooner than they should. The 2016 Warwick Agreement, an international consensus statement, defined FAI syndrome as a motion- or position-related clinical disorder involving a triad: characteristic symptoms, positive clinical signs on examination, and supporting imaging findings.¹ That definition matters. Abnormal hip shape shows up on imaging in plenty of people with no pain at all, so a scan alone does not make the diagnosis. It is the combination of symptoms, examination, and imaging that does.

The typical picture is deep groin or front-of-hip pain, often described as a pinch rather than an ache, provoked by deep flexion: a low squat, sitting for long stretches, getting in and out of a car, or bringing the knee up and across the body. Some people notice a catch or a feeling of the hip not gliding smoothly. Pain can also show up at the side of the hip or into the buttock.

When the hip is the real story

Here is where it gets interesting for anyone chasing stubborn knee or back symptoms. Regional interdependence is the idea that a problem in one area can produce symptoms in a remote, seemingly unrelated region, and that treating the distant driver often relieves the presenting complaint.² The hip sits right in the middle of the chain, so when it moves poorly, the segments above and below tend to pick up the slack.

A hip that cannot rotate or flex fully will often borrow motion from the low back, which may become the site that feels tight or sore even though it is compensating rather than failing. Downstream, restricted hip movement and altered muscle control can change how the knee tracks and loads, so a knee that keeps flaring up despite knee-focused treatment sometimes settles only once the hip is addressed. This is why a thorough assessment looks above and below the painful area rather than staring at the symptom alone. We explore this pattern more broadly in our article on regional interdependence and whole-body assessment.

What the evidence says about treatment

This is the part where FAI has been studied unusually well, which lets us speak with more confidence than for many hip conditions. The central question has been whether people do better with hip arthroscopy, a keyhole surgery to reshape the joint, or with structured physiotherapy-led rehabilitation.

The UK FASHIoN trial, a multicentre randomized controlled trial published in The Lancet, compared hip arthroscopy against a personalized, progressive, physiotherapist-led rehabilitation program in patients with FAI syndrome.³ Both groups improved. Surgery showed a modest advantage in hip-related quality of life at follow-up, but the important nuance is that structured rehabilitation produced meaningful improvement for many patients without an operation. In other words, conservative care is a legitimate first-line option, not merely a waiting room before inevitable surgery.

What does that rehabilitation involve in practice? Broadly:

• Building hip strength and control, particularly around the glutes and deep hip stabilizers, so the joint is supported through its range.
• Improving how you move in the positions that provoke symptoms, including squat depth and technique, so the impingement is less frequently loaded.
• Managing load sensibly, dialing provocative activities down enough to calm things while gradually rebuilding tolerance. There are no bad movements here, only too much too soon.
• Addressing the neighbours, since the back and knee that have been compensating usually need attention too.

Where surgery fits

Surgery remains a reasonable consideration for people whose symptoms persist despite a genuine, well-run course of rehabilitation, and the decision is individual. The point is not that surgery never helps; it is that a good conservative trial is worthwhile first, because a meaningful share of people improve enough that they never need the operating room. A frank conversation about goals, activity demands, and how the hip has responded to loading should guide that choice, ideally alongside a surgeon when the question is genuinely on the table.

The practical takeaway

If you have front-of-hip or groin pain that pinches at the bottom of a squat or after long sitting, that is worth assessing on its own terms. And if you have a knee or a low back that keeps flaring despite focused treatment, it is worth asking whether the hip is quietly steering the ship. Hips are easy to overlook precisely because they so often speak through other joints. Looking at the whole chain, and giving progressive rehabilitation a real chance, is usually where the answer lives.

References

1. Griffin DR, Dickenson EJ, O'Donnell J, et al. The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med. 2016;50(19):1169-1176.
2. Sueki DG, Cleland JA, Wainner RS. A regional interdependence model of musculoskeletal dysfunction: research, mechanisms, and clinical implications. J Man Manip Ther. 2013;21(2):90-102.
3. Griffin DR, Dickenson EJ, Wall PDH, et al. Hip arthroscopy versus best conservative care for the treatment of femoroacetabular impingement syndrome (UK FASHIoN): a multicentre randomised controlled trial. Lancet. 2018;391(10136):2225-2235.

Dr. Michael Minenna D.C., B.Sc., SFMA, FMS