Femoroacetabular impingement

• Deep groin pain is more typical than side-of-hip pain.
• Symptoms often build with sitting, squatting, lunging or pivoting.
• Ultrasound can help with associated tendon or injection decisions, but the diagnosis remains primarily clinical and imaging-led.

Femoroacetabular impingement (FAI) describes a shape-related conflict between the ball and socket of the hip. It commonly presents as deep groin pain during flexion, twisting, pivoting or prolonged sitting, particularly in active adults who load the hip heavily.

Typical presentation

Patients often report pinching or catching deep in the groin, especially with sitting low, getting out of a car, twisting, kicking or loaded flexion work at the gym. Some people also describe stiffness after sitting and reduced confidence with rapid direction change.

The symptoms can overlap with labral irritation, hip osteoarthritis, iliopsoas-related pain and adductor-related groin pain, which is why the detail of the story matters.

Why it happens

FAI is usually discussed in terms of cam and pincer morphology, although many symptomatic patients have a mixed pattern. The important clinical point is that repeated flexion and rotational loading can irritate the front of the joint, labrum and nearby soft tissues when load exceeds what the hip currently tolerates.

Not every shaped hip is painful. The diagnosis is strongest when the symptom pattern, movement findings and imaging fit together.

Assessment and differential diagnosis

Assessment focuses on where the pain is felt, which movements reproduce it, whether there is mechanical catching, and whether stiffness or loss of hip rotation is part of the picture. Differential diagnoses include labral tear, hip osteoarthritis, iliopsoas tendinopathy, adductor-related groin pain and stress-related bone pain.

Deep night pain, severe pain at rest or inability to weight bear warrant a more urgent review.

Where ultrasound helps

Ultrasound does not diagnose bony impingement as directly as X-ray or MRI, but it can be very useful when the main irritability seems to sit in the iliopsoas tendon, rectus femoris origin, adductor tendons or an effused anterior joint recess. It also allows precise image-guided injection when a joint injection is clinically indicated.

Treatment strategy

Treatment usually starts with load modification, hip control work, strengthening, mobility where appropriate and helping patients identify which positions are repeatedly provoking symptoms. The aim is not to avoid flexion forever, but to calm the hip and rebuild tolerance.

Joint injection may be discussed when pain is clearly intra-articular and the main goal is to reduce pain to progress rehabilitation or to clarify how much of the symptoms are genuinely joint-driven.

Evidence strength summary

Current evidence supports targeted rehabilitation for many symptomatic patients, while surgical opinions are usually reserved for carefully selected cases with persistent mechanical symptoms and imaging that genuinely matches the clinical picture.

Page-specific FAQs

Harvard references

• Clinical references for this topic are collated in the Clinical Evidence Library.
• Where ultrasound-guided injection is discussed, see the clinician review on accuracy of ultrasound-guided injections.