The symptom pattern that points to FAI

A familiar pattern brings many patients to clinic: groin discomfort that flares when sitting for long periods or getting out of a car, an audible click or catching sensation when rotating the hip, and a stiffness after sport or exercise that takes longer than it used to settle. Taken individually, each of these symptoms has a long differential. Taken together, they describe a recognisable triad — anterior groin pain (patients often cup the front of the hip and groin with a curved hand, a gesture clinicians call the 'C-sign'), hip clicking or catching, and restricted internal rotation, particularly at 90° of hip flexion.

The combination matters more than any single feature. Clicking alone — a snap or clunk felt near the hip or groin — is commonly caused by the iliopsoas tendon or iliotibial band catching across a bony prominence, and in the absence of pain or restricted rotation it is usually benign. It is when clicking accompanies groin pain and a loss of rotation that femoroacetabular impingement (FAI) or a labral tear moves up the list.

If a GP has already examined the hip, they may have performed the FADIR test — passive flexion of the hip to 90°, followed by adduction and internal rotation. Pain reproduced in the groin by this manoeuvre is the clearest clinical signal that the symptoms deserve closer attention than conservative management alone can provide.

What's happening inside the hip joint

Inside the hip, the femoral head (the ball) sits within a deep cup called the acetabulum, lined by a ring of fibrocartilage — the labrum. Think of the labrum as a rubber seal: it deepens the socket, cushions contact between the bones, and maintains the pressurised fluid environment that allows smooth, low-friction movement. When that seal is intact, the joint distributes load evenly across a wide area.

In FAI, the problem begins with bone shape. A cam lesion is a subtle bony prominence on the femoral head-neck junction — the ball is no longer quite round. A pincer lesion is excess bone around the acetabular rim — the cup overhangs too far. Some people have both. During everyday movements that involve hip flexion and rotation — deep squatting, getting into a low car, pivoting — the altered geometry forces the abnormal bone to press and shear against the labrum repeatedly.

Over time, this repetitive friction erodes the labrum at its most vulnerable point (typically the anterosuperior rim), and the damage extends progressively to the underlying articular cartilage. Because the labrum has very limited capacity to heal on its own, the natural course without intervention tends to be gradual rather than sudden — which is partly why many patients tolerate symptoms for months before seeking assessment.

The long-term significance was described by Reinhold Ganz and colleagues in 2003, who proposed unaddressed FAI as a leading mechanism for early hip osteoarthritis in non-dysplastic hips. This affects young and middle-aged active adults — not only competitive athletes — which is why timely specialist assessment matters rather than indefinite watchful waiting.

Starting with conservative care

Supervised physiotherapy is the appropriate starting point for most patients with FAI-related groin pain — beginning there is the clinically correct first move, not a detour. A 2025 scoping review of conservative management for FAI syndrome confirmed that structured rehabilitation should precede any escalation in the absence of red-flag mechanical symptoms such as locking or giving way.

What distinguishes effective conservative care from generic advice is specificity. Good physiotherapy for FAI targets the hip rotators and flexors, builds progressive load on the gluteal muscles, develops core stability, and trains neuromuscular control — the aim being to offload the impingement zone and reduce the compressive forces that irritate the labrum. 'Rest and see' is not a treatment programme.

Six to twelve weeks is the evidence-supported trial window most specialists work to. If symptoms have not shown meaningful improvement within this period, that absence of progress is a referral trigger — not a reason to extend the programme indefinitely.

During this window, three signals are worth tracking: whether restricted internal rotation is improving, whether groin pain with specific movements (sitting for long periods, rotating, deep squatting) is reducing, and whether any mechanical catching or giving-way is occurring. It is those findings — not the passing of time alone — that shape the next clinical conversation.

Signs that GP care is no longer enough

Four clinical findings, in particular, indicate that the next step is specialist assessment rather than continued GP management.

Mechanical symptoms at any stage. Locking, giving way, or a true catching sensation — where the hip feels as though something has snagged or jammed mid-movement — are distinct from a simple audible click. An audible snap without pain or restriction may reflect iliopsoas or iliotibial band snapping and does not require urgent onward referral on its own. A locking or giving-way episode does.

No clear improvement within the physiotherapy window. If the 6–12 week trial produces a plateau or deterioration rather than meaningful progress, that is a signal to escalate rather than extend the same programme.

Functional restriction in daily life or sport. Groin pain that limits sitting for more than a short period, stair-climbing, getting in and out of a car, or athletic performance has crossed the threshold where intra-articular assessment becomes appropriate.

Significantly restricted internal rotation at 90° of hip flexion. A positive FADIR test — groin pain provoked by passive flexion, adduction, and internal rotation — in combination with the symptom pattern above substantially strengthens the case for referral.

There is a fifth, less tangible reason to refer rather than wait: the groin pain differential is genuinely difficult. Adductor tendinopathy, osteitis pubis, and inguinal pathology overlap substantially with FAI in presentation. A GP, without access to image-guided examination or intra-articular injection as a diagnostic tool, may reasonably struggle to distinguish them. When the picture remains unclear after a proper trial of conservative care, specialist correlation is the appropriate next step — not an extended wait, particularly in younger active patients for whom the consequences of delayed assessment are, as discussed, meaningful.

Why a normal MRI doesn't rule it out

A reassuring MRI report does not close the investigation when clinical suspicion remains high — and this is one of the points patients find most confusing.

Standard MRI detects roughly half of labral tears. Published data place sensitivity at approximately 55% and specificity between 38% and 46% for labral pathology, meaning a normal scan can genuinely miss a significant tear. The scan is a useful starting point, but it is one input among several — not a verdict on whether the hip is the pain source.

What a specialist adds in this situation is clinical correlation: weighing the symptom pattern, the FADIR examination findings, and the imaging together rather than treating the report in isolation. If the clinical picture still points strongly to intra-articular pathology, the appropriate next step is MR arthrography — a contrast-enhanced scan with meaningfully higher diagnostic yield than standard MRI — rather than discharging the patient on the basis of a normal scan.

There is also a practical intermediate: an image-guided intra-articular injection (corticosteroid or similar) serves a dual purpose. If it produces clear relief, that response confirms the joint as the pain source. If it does not, it helps redirect the investigation. In either case, it is a diagnostic step as much as a therapeutic one — and it is a decision best made by a specialist who can interpret the response in context.

What specialist assessment and the pathway ahead look like

A first appointment with a hip specialist is less daunting than many patients expect. The consultation centres on clinical synthesis: structured history, provocation testing — including FADIR — assessment of rotation and movement range, and review of any imaging already obtained. Where that imaging is a standard MRI, the specialist will consider whether MR arthrography or an image-guided diagnostic injection adds more useful information before committing to a treatment direction.

For patients who have completed a supervised physiotherapy programme without meaningful improvement — typically after three months or more — the evidence supports escalation. A 2025 meta-analysis of 21 randomised controlled trials involving 1,799 patients found hip arthroscopy produced significantly better outcomes than continued conservative care: Harris Hip Score improved by 6.5 points at 12 months and iHOT-12 by 9.8 points at 24 months. These are clinically meaningful differences, and they inform the threshold at which arthroscopy moves from an option to a recommendation.

Longer-term data reinforce why the timing of referral matters. In a 10-year follow-up series, approximately 79% of patients treated arthroscopically avoided total hip replacement — though outcomes were meaningfully worse in those with higher-grade cartilage damage at the time of surgery and in older patients. Delay that allows cartilage to deteriorate worsens the prognosis for surgical management when it eventually becomes necessary.

For those who have reached this decision point, Professor Paul Y. F. Lee provides hip joint-preservation assessment and arthroscopic management at London Cartilage Clinic on Harley Street; appointments can be arranged via londoncartilage.com.

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