Femoroacetabular impingement (FAI)

What is femoroacetabular impingement?

FAI describes a shape collision in the hip joint: Bone attachments or shape variations on the femoral neck (cam) or on the socket (pincer) lead to impact during flexion, internal rotation and adduction. This can irritate or damage the labrum (joint lip) and cartilage. Not every anatomical variant causes symptoms - the combination of shape, movement and stress is crucial.

• Cam type: Thickening/asphericity at the head-neck transition, reduces head-neck offset.
• Pincer type: roofing/over-rotation of the socket, contact of the femoral neck with the edge of the socket.
• Mixed type: Combination of both mechanisms (most common variant).

Anatomy and mechanics of the hip

The hip is a ball-and-socket joint made up of the head of the thigh (femoral head) and the socket (acetabulum). The labrum increases the socket depth and stabilizes the joint. Cartilage covers the joint surfaces and enables low-friction movement. A healthy head and neck offset prevents collisions during movements such as squatting, sprinting or changing direction.

• Labrum: fibrocartilage ring, sealing and stabilizing.
• Articular cartilage: shock absorber and sliding surface.
• Capsule/ligaments: passive-stabilizing structures, relevant for capsular tension and laxity.

FAI types: Cam, Pincer and mixed forms

Typing helps to classify symptoms and determine therapy goals. Cam impingement often damages the anterolateral cartilage-labrum complex first, whereas in the pincer type, the labrum is more likely to suffer impingement. Mixed forms are the most common.

• Cam: Increased alpha angle, reduced head and neck offset.
• Pincer: Coverage (e.g. deep pan, retroversion), positive crossover sign.
• Mixed type: elements of cam and pincer combined.

Typical symptoms

FAI usually manifests itself as deep groin pain, often stabbing during flexion and internal rotation. Pain when starting to sit, restricted movement and a feeling of “blocking” are common. Pain may radiate to the thigh or buttocks.

• Stress-related groin or hip pain, e.g. B. when sitting in the car, squatting, putting on socks.
• Sporting triggers: football, hockey, dance, martial arts, CrossFit.
• Clicking/snapping in the groin (indicative of labral irritation).
• Occasionally pain laterally (differentiation from coxa saltans externa).

Causes and risk factors

FAI arises from the interaction of morphology and loading. Form variants can be congenital or develop in adolescence under high levels of sporting stress. Movement patterns, muscular imbalances and limited hip mobility increase the conflict.

• Shape variants (cam/pincer), hip dysplasia variants or socket retroversion.
• High levels of training in adolescence with repetitive bending/rotating movements.
• Restricted movement (internal rotation), limited hip extension, lumbopelvic imbalance.
• Previous surgeries or labrum/cartilage damage.

Diagnostics: structured and targeted

Diagnosis is based on history, clinical examination and imaging. It is important to record symptoms, everyday requirements and sporting goals. Not every bony variant in the X-ray is pathogenic - the clinic has priority.

Differential diagnoses must be considered, including: Groin athlete syndrome, adductor tendinopathy, coxa saltans externa or inflammatory causes.

Differential diagnoses

• Labrum lesion of the hip (often associated).
• Coxarthrosis (degenerative changes that occur over a long period of time).
• Hip dysplasia (altered socket coverage).
• Hip capsulitis/synovitis (inflammatory irritation).
• Coxa saltans externa (lateral snap hip, iliotibial tract).
• Psoas tendinopathy, adductor tendinopathy, groin athlete syndrome.
• Coxitis (septic/inflammatory, urgent clarification in case of fever/acute pain peak).

Conservative therapy: the first step

In most cases, structured, conservative treatment is the first choice. The aim is to reduce pain, improve function and adjust the load in order to reduce mechanical impact. An interdisciplinary approach (doctor, physiotherapy, training) makes sense.

• Activity adaptation: temporary reduction of deep flexion angles, explosive changes of direction and sitting with strong hip flexion.
• Physiotherapy: Improving internal rotation/extension, lumbopelvic control, strengthening gluteal muscles, deep hip rotators, core stability.
• Technique and movement coaching: sport-specific modification (e.g. landing technique, cutting movements).
• Manual therapy and mobilization: addressing capsular tension, soft tissue techniques.
• Targeted home exercises: 3–5x/week, progressive; Documentation of pain/strain.
• Medication: time-limited NSAIDs if needed; Pay attention to accompanying factors (stomach/kidneys).
• Load control: return-to-run/return-to-sport protocols with step-by-step plan.

Injections and regenerative procedures: when does it make sense?

Injections can temporarily relieve pain or support diagnostics in selected patients. They do not replace exercise therapy. The benefit depends on the symptoms and accompanying findings (e.g. labral irritation).

• Intra-articular local anesthesia (diagnostic): Differentiation of intra-articular and extra-articular pain.
• Corticosteroid injection: may provide short-term relief; cautious use, careful indication.
• Hyaluronic acid: evidence in the hip heterogeneous; Decision on a case-by-case basis.
• PRP (platelet-rich plasma): evidence remains limited for hip/FAI; only be considered after information and with a clear objective.

We discuss benefits, risks and alternatives transparently. There is no guarantee that you will continue to be free of symptoms.

Surgical therapy: indications and process

If relevant complaints and functional deficits persist despite consistent conservative therapy and imaging shows appropriate morphological findings, hip arthroscopy can be considered. The aim is to reduce conflict (cam resection, pincer correction) and to treat accompanying damage (labral refixation/reconstruction, cartilage smoothing).

• Indications: persistent groin pain, positive clinical tests, correlative imaging, lack of response to conservative measures.
• Procedure: arthroscopic cam/pincer correction, labrum refixation, capsular management (possibly capsular plication in case of laxity).
• Follow-up treatment: partial weight-bearing and movement limits initially; early functional physiotherapy; gradual increase.
• Risks: Nerve irritation, stiffness, persistence of symptoms, thrombosis, heterotopic ossifications; individual risk will be discussed in the informative discussion.
• Return to Sport: often after 3-6 months, depending on initial findings, healing process and type of sport.

Surgery can reduce symptoms and improve function, but does not guarantee complete and permanent freedom from symptoms. Decisions are always individual.

Course and prognosis

Many patients achieve significant relief with a structured conservative program. If there is pronounced morphology, a long course of symptoms or relevant labral/cartilage damage, the prognosis may be more cautious. Untreated, stress-induced conflicts can promote degenerative changes; However, this does not necessarily result in a progression to osteoarthritis.

• Early adaptation of training and technique improves the chances of complaint control.
• Realistic goals: pain reduction, functional gain, resilient activity level.
• Regular re-evaluation and adjustment of the plan are important.

Everyday life, work and prevention

Small changes in everyday life can have big effects. Temporarily avoid deep squatting, take breaks when sitting and maintain a hip-friendly posture.

• Sitting hygiene: knees not well above hip height; stand up regularly, stretch your hips.
• Warm-up and mobility: Focus on hip extension and internal rotation.
• Strength training: emphasizes gluteus maximus/medius, core; slow progression.
• Technique training: landings, changes of direction, hip-knee axis.
• Load control: 10-15% rule for weekly increases, pain scale as a guideline (e.g. tolerable up to 3/10, not increasing).

When should I seek medical advice?

• Persistent groin pain for several weeks despite rest/exercises.
• Severe limitation of hip movement.
• Feeling of blocking, snapping with pain, feeling of instability.
• Acute severe pain after trauma, inability to bear weight.
• Fever, night pain or significant redness/warmth (suspected inflammatory cause).

We will advise you individually in Hamburg, create a diagnostic plan and discuss the next steps – conservatively first.