• The used traction technique was well tolerated by most patients. • The used traction technique almost consistently achieved separation of cartilage layers. • Traction MR arthrography enabled accurate detection of chondral and labral lesions.

Objectives: Imaging assessment for the clinical management of femoroacetabular impingement syndrome (FAIS) remains controversial because of a paucity of evidencebased guidance and notable variability in clinical practice, ultimately requiring expert consensus. The purpose of this agreement is to establish expert-based statements on FAIS imaging, using formal techniques of consensus building driven by relevant literature review. Methods:The validated Delphi method and peer-reviewed literature were used to formally derive consensus among 30 panel members (21 musculoskeletal radiologists and 9 orthopedic surgeons) from 13 countries.Forty-two questions were agreed on, and recent relevant seminal literature was circulated and classified in five major topics ("General issues", "Parameters and reporting", "Radiographic assessment", "MRI evaluation" and "Ultrasound") in order to produce answering statements.The level of evidence was noted for all produced statements and panel members were asked to score their level of agreement with each statement (0 to 10) during iterative rounds. Either "group consensus", "group agreement" or "no agreement" was achieved.Items near consensus were further queried using 4 moderated group sessions and in 4 Delphi rounds.Results: Forty-five statements were generated and group consensus was reached for 43 (95.7%). Seventeen of these statements were selected as most important for dissemination in advance. There was no agreement for the two statements pertaining to "Ultrasound". Conclusion:The first international Delphi-based consensus for the imaging assessment of FAIS was developed. The resulting consensus can serve as a tool to reduce variability in clinical practices and guide further research for the clinical management of FAIS. Key Points• FAI imaging literature is extensive although often of low level of evidence.• Radiographic evaluation with a reproducible technique is the cornerstone of hip imaging assessment.• MRI with a dedicated protocol is the gold standard imaging technique for FAI assessment.

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Aims: Imaging assessment for the clinical management of femoroacetabular impingement (FAI) syndrome is controversial because of a paucity of evidence-based guidance and notable variability among practitioners. Hence, expert consensus is needed, because standardised imaging assessment is critical for clinical practice and research. We aimed to establish expert-based statements on FAI imaging by using the formal methods of consensus-building. This is the second part of a three-part consensus series, and focuses on 'General issues' and 'Parameters and reporting'. Methods:The Delphi method was used to formally derive consensus among 30 panel members from 13 countries. Forty-four questions were agreed upon, and relevant seminal literature was circulated and classified in major topics ('General issues', 'Parameters and reporting', 'Radiographic assessment', 'Magnetic resonance imaging (MRI)' and 'Ultrasound') to produce answering statements. The level of evidence was noted for all statements, and panel members were asked to score their level of agreement (0-10). Either 'group consensus', 'group agreement', or 'no agreement' was achieved.Results: Forty-seven statements were generated and group consensus was reached for 45. Twenty-five statements pertaining to 'General issues' (nine addressing diagnosis, differential diagnosis and postoperative imaging) and 'Parameters and reporting' ( 16addressing femoral/acetabular parameters) were produced. Conclusions:The first international Delphi-based consensus on FAI imaging was developed. The available evidence was reviewed critically, recommended criteria for diagnostic imaging highlighted, and the roles of different imaging parameters assessed.The resulting statements can serve as a tool for practitioners working with hip-related pain to reduce clinical variability and guide further research for FAI management. Key points Radiographic evaluation (anteroposterior radiograph of the pelvis and a lateral view of the hip, preferably a Dunn 45° view) with a reproducible methodology is the cornerstone of hip-imaging assessment and minimum imaging study that should be performed when assessing adult patients for FAI. In selected cases, cross-sectional imaging is warranted because MRI with a dedicated protocol is the 'gold standard' imaging modality for the comprehensive evaluation, differential diagnoses assessment, and surgical planning of FAI. For acetabular morphology, coverage (centre-edge angle of Wiberg and acetabular index) and version (crossover, posterior wall, and ischial spine signs) should be assessed routinely. On the femoral side, the morphology of the head-neck junction (alpha angle and offset), neck morphology (neck-shaft angle) and torsion (antetorsion angle) should be assessed routinely. ClinicalRelevance  Imaging assessment for FAI is unstandardised because of a paucity of evidencebased guidance and lack of consensus among experts on which imaging modalities, diagnostic criteria, and parameters should be used/assessed routinely. This Delphibased consensus, aims t...

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