Femoroacetabular Impingement

History: groin pain is the dominant symptom - deep, anterolateral, with the patient often demonstrating the "C-sign" by cupping the anterolateral hip. Pain is activity-related, worse with prolonged sitting, rising from chairs, getting in and out of cars, squatting, twisting, and sports involving hip flexion and rotation. Catching, clicking, locking, or giving way suggests labral involvement. Symptoms may be insidious or follow a specific event in sport. Bilateral morphology is common; ask about contralateral symptoms. Ask about previous hip conditions (Perthes, SUFE), sporting history during adolescence, and previous hip injury.

Examination:

• •FADIR (Flexion, ADduction, Internal Rotation): the most important clinical test. Flex the hip to 90 degrees, then adduct and internally rotate - reproduction of deep anterolateral groin pain is positive. High sensitivity, lower specificity. Negative FADIR makes FAI unlikely
• •FABER (Flexion, ABduction, External Rotation / Patrick test): figure-of-four position. Groin pain suggests hip joint pathology; posterior buttock pain suggests SIJ pathology
• •Internal rotation in flexion: typically reduced and painful. Compare with the opposite hip - asymmetry is more clinically useful than absolute values
• •Log roll: gentle rotation with the knee extended - pain suggests intra-articular pathology
• •Stinchfield (resisted SLR): active hip flexion against resistance reproduces groin pain

Examine the lumbar spine, SIJ, and adductors - groin pain has a broad differential in young athletes.

Differentials: hip OA (older patient, established radiographic OA), labral tear without FAI morphology, athletic groin pain (adductor-related, often coexists), iliopsoas tendinopathy or snapping hip, femoral neck stress fracture, AVN, lumbar radiculopathy (L2-L3), and SUFE in adolescents.

FAI syndrome is a clinical-radiological diagnosis. Clinical findings must correlate with imaging - morphology alone is insufficient.

• •Plain radiographs (AP pelvis + lateral hip view): first-line imaging. AP pelvis assesses joint space, acetabular morphology (crossover sign for retroversion, LCEA for over-coverage), and femoral head-neck offset. A Dunn 45 or 90-degree lateral, or cross-table lateral, best demonstrates the cam lesion. The alpha angle is measured on the lateral view, with values over approximately 60 degrees suggesting cam morphology. Assess for joint space narrowing (established OA), subchondral cysts, and os acetabuli
• •Cross-sectional imaging (MRI with or without arthrogram, CT): not routinely arranged in primary care. MR arthrogram has higher sensitivity for labral tears and cartilage delamination. CT provides detailed 3D bony morphology for surgical planning
• •Diagnostic intra-articular injection: image-guided local anaesthetic injection can confirm the hip as the pain source when the picture is unclear
• •Bloods: not routinely indicated; consider inflammatory markers if inflammatory arthritis or infection is suspected

Conservative-first. Guided by the Warwick Agreement (2016), UK FASHIoN trial, NICE procedural guidance, and UK specialist consensus.

Conservative management (first-line):

• •Education: explain the condition and the meaning of imaging findings; reassure that morphology alone does not predict symptoms
• •Activity modification: temporarily reduce aggravating activities; modify rather than stop; maintain fitness
• •Analgesia: simple analgesia or 2-4 weeks of oral NSAIDs for flare symptom relief
• •Physiotherapy-led rehabilitation (the cornerstone): individualised, goal-based. The UK FASHIoN trial termed this Personalised Hip Therapy (PHT). Key components: progressive strengthening of gluteus maximus, gluteus medius, deep hip external rotators, and adductors; core and pelvic stability; functional movement control of hip, pelvis, lumbosacral spine, and lower limb; minimal stretching, only within pain-free range; kinetic chain assessment and correction
• •Intra-articular injection: image-guided corticosteroid with or without local anaesthetic for short-term symptom relief and diagnostic value. Supports rehabilitation, does not replace it

Referral: to a hip specialist if symptoms persist despite a reasonable trial of structured conservative management (reviewed at around 3 months), significant mechanical symptoms not improving, diagnostic uncertainty, elite athlete needing expedited assessment, or suspected established OA (joint space narrowing).

Surgical options:

• •Hip arthroscopy is the commonest UK intervention for FAI syndrome. Per NICE, current evidence is adequate for short and medium-term symptom relief with specialist expertise and governance arrangements. Allows cam resection (femoral osteochondroplasty), pincer correction (acetabular rim trimming), labral repair or reconstruction, and cartilage procedures
• •UK FASHIoN trial (2018): arthroscopy provided greater improvement in hip-related quality of life than PHT at 12 months, though both groups improved. Patient selection is critical
• •Established OA exclusion: joint space under 2 mm on plain radiograph is a common UK exclusion criterion for arthroscopy because outcomes are poor; these patients should be counselled about eventual hip replacement
• •Open surgical hip dislocation is rarely performed in UK practice. Joint replacement is reserved for end-stage OA

Conservative rehabilitation (PHT framework):

Phase 1 (pain-dominant, 0-6 weeks): activity modification; avoidance of impingement positions (deep flexion, combined flexion / adduction / internal rotation). Isometric gluteal and core activation. Maintain cardiovascular fitness - cycling with a raised seat height is the safest early option; avoid breaststroke kick. Address lumbopelvic dysfunction.

Phase 2 (loading, 6-12 weeks): progressive resistance training targeting gluteus maximus, gluteus medius, deep hip external rotators, and adductors. Core and pelvic stability progression. Functional movement control - squat, lunge, step patterns. Stretching only within pain-free range.

Phase 3 (functional and sport-specific, 12+ weeks): progressive return to sport - running, cutting, kicking, change of direction. Sport-specific drills. Kinetic chain assessment. Graduated return to competition.

Post-arthroscopy: surgeon- and procedure-dependent. Protected weight-bearing 2-4 weeks (labral repair may need longer). Early ROM within prescribed limits. Progressive strengthening from 4-6 weeks. Return to sport typically 4-6 months for cam resection alone, 6-9 months for labral repair; timing is individualised on rehab milestones. Compliance with rehabilitation is the strongest predictor of outcome.

• •Warwick Agreement on FAI Syndrome (Griffin et al., BJSM 2016): international consensus defining FAI syndrome as the triad of symptoms + clinical signs + imaging morphology.
• •UK FASHIoN trial (Griffin et al., Lancet 2018): multi-centre RCT showing hip arthroscopy produced greater 12-month improvement in hip-related quality of life than Personalised Hip Therapy, with both groups improving.
• •NICE Interventional Procedures Guidance on hip arthroscopy: current evidence is adequate for short and medium-term symptom relief in appropriately selected patients with specialist expertise and governance arrangements.
• •Notzli alpha angle (2002) and Tonnis acetabular measurements: standard radiographic FAI metrics; alpha angle over approximately 60 degrees on lateral view suggests cam morphology.
• •iHOT-33, HAGOS, and NAHS: validated FAI patient-reported outcome measures.
• •Ganz et al. (Clin Orthop Relat Res 2003): foundational work establishing FAI as a pathway to hip OA.

• •FAI syndrome = symptoms + clinical signs + imaging morphology (Warwick Agreement). All three must be present. Morphology alone is NOT a diagnosis.
• •Cam = femoral side (pistol grip deformity, young males, anterolateral bump, alpha angle over 60 degrees, shears labrum). Pincer = acetabular side (over-coverage, middle-aged females, crushes labrum, crossover sign, LCEA over 40 degrees). Mixed is commonest.
• •FADIR is the key clinical test - high sensitivity. Negative FADIR makes FAI unlikely. The crossover sign on AP pelvis indicates acetabular retroversion (pincer).
• •In an adolescent with groin pain and restricted internal rotation, SUFE must be excluded before considering FAI. The pathognomonic sign is obligatory external rotation during passive hip flexion.
• •Athletic groin pain (adductor-related) commonly coexists with FAI - always examine the adductors.
• •UK FASHIoN trial: arthroscopy superior to PHT at 12 months but both groups improved. Established OA (joint space under 2 mm) is a common UK arthroscopy exclusion - outcomes are poor.