Hip Arthroscopy for
Femoroacetabular Impingement

What is femoroacetabular impingement?

Femoroacetabular impingement (FAI) syndrome occurs when the ball (femoral head) and socket (acetabulum) of the hip have a shape that causes abnormal, repetitive contact during normal hip motion — particularly deep flexion and rotation, as in squatting, pivoting, or sitting low. Over time, this contact damages the acetabular labrum, the ring of cartilage that seals and stabilises the joint, and can damage the adjacent articular cartilage.

There are two underlying bone shape abnormalities, and most patients have some combination of both:

Type	Where the abnormality is	What it looks like
Cam	Femoral head–neck junction	Extra bone reduces the normal offset, so the head is not perfectly round
Pincer	Acetabular rim	The socket over-covers the femoral head, most often at the front rim
Mixed	Both	Cam and pincer morphology present together — the most common pattern

It is important to note that cam or pincer morphology on an X-ray is common in the general population and does not, by itself, mean surgery is needed. FAI is a clinical syndrome — the diagnosis requires the combination of hip or groin pain, positive impingement signs on examination, and imaging findings that correspond to the symptoms.

How the diagnosis is made

FAI syndrome is frequently mistaken for a groin strain, hip flexor tendinopathy, or referred lower back pain, partly because it presents in active, otherwise healthy people and partly because plain X-rays alone are easy to misread. A proper work-up starts with a focused history — pain with prolonged sitting, deep squatting, getting in and out of a car, or a catching/clicking sensation is typical — followed by examination manoeuvres such as the anterior impingement test (flexion, adduction, internal rotation), which aims to reproduce the patient's exact pain.

Imaging then confirms or refutes the clinical impression. Weight-bearing pelvic X-rays assess alpha angle, acetabular coverage, and joint space. MRI, ideally with intra-articular contrast (MR arthrogram), is the most reliable way to characterise labral and cartilage damage. Occasionally a diagnostic image-guided injection is used to confirm that the hip joint itself, rather than a surrounding soft-tissue structure, is the source of pain — a useful step when the clinical picture is mixed.

Who is a candidate for hip arthroscopy

Hip arthroscopy is considered when symptomatic FAI has not responded to a genuine trial of non-surgical treatment — activity modification, physiotherapy focused on hip and core control, and in some cases an intra-articular injection to confirm the joint as the pain source. It is not the first step for a newly diagnosed, mildly symptomatic hip.

Joint space narrowing and existing osteoarthritic change are the strongest predictors of a poor result from arthroscopy — in an arthritic hip, decompressing the bone conflict does not reliably relieve pain, and joint replacement becomes the more appropriate discussion. Patient selection is the single biggest factor separating a good outcome from a disappointing one.

What the trial evidence shows

Hip arthroscopy for FAI is now supported by randomised evidence, which is relatively unusual in orthopaedic surgery. The UK FASHIoN trial randomised patients with FAI syndrome to arthroscopic surgery or a structured physiotherapist-led programme ("personalised hip therapy").

A more recent multilevel meta-analysis of randomised trials (Ramadanov et al., Bone & Joint Open, 2025) pooling FASHIoN and subsequent RCTs found a broadly similar pattern: hip arthroscopy produces greater improvement than structured conservative treatment for FAI syndrome in the short-to-medium term, but conservative treatment is not without benefit and is a reasonable first step for many patients, particularly those with lower-grade morphology or lower symptom severity.

Longer-term data are also reassuring for appropriately selected patients. A systematic review of studies with minimum 5-year follow-up (Jan et al., Arthroscopy, 2023) found that clinically significant improvement was generally maintained, though the proportion of patients reaching the highest benchmarks (substantial clinical benefit) declined somewhat compared with 1–2 year outcomes, and older age plus greater baseline joint degeneration were the most consistent predictors of a worse long-term result.

What the surgery involves

Hip arthroscopy is performed through small portals (usually 2–3, each under a centimetre) using traction to distract the joint and create working space. Under arthroscopic visualisation:

Femoroplasty reshapes the cam lesion at the head-neck junction, restoring normal offset and clearance during hip flexion. Acetabuloplasty trims excess acetabular rim in pincer morphology, correcting over-coverage. The labrum is assessed and, where the tissue quality allows, repaired back to the acetabular rim with suture anchors rather than removed.

Recovery

Hip arthroscopy is typically a day-case or overnight-stay procedure. Protected weight-bearing on crutches is generally required for 2–4 weeks depending on how much bony reshaping was performed, followed by a structured physiotherapy programme focused first on restoring range of motion and controlling swelling, then on progressive strengthening of the hip and core. Most patients return to low-impact daily activity by 6–8 weeks and to sport-specific training in the 3–5 month range, though full return to pivoting or contact sport is often closer to 5–6 months and should be guided by functional testing rather than the calendar alone.

Risks and limitations

As with any surgery, hip arthroscopy carries risks: traction-related nerve symptoms (usually transient, affecting the pudendal or lateral femoral cutaneous nerve distribution), instrument-related cartilage injury, and in a minority of cases, incomplete correction of the bony morphology requiring revision. Reported revision arthroscopy rates in the published literature are generally in the range of 5–10%, and are higher in patients with borderline dysplasia or under-corrected morphology. Conversion to total hip replacement can occur, particularly in older patients or those with pre-existing joint space narrowing — which is exactly why imaging and patient selection are emphasised so heavily before recommending surgery.

If you have hip pain and are unsure whether it reflects FAI, a labral tear, early arthritis, or something else entirely (such as a muscle strain or referred spinal pain), a clinical assessment with weight-bearing X-rays is the appropriate starting point before any discussion of arthroscopy.