This is EMRad, a series aimed at providing “just in time” approaches to commonly ordered radiology studies in the emergency department [1]. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. Next up: the hip.

Learning Objectives

  1. Interpret traumatic hip x-rays using a standard approach
  2. Identify clinical scenarios in which an additional view might improve pathology diagnosis

Why the hip matters and the radiology rule of 2’s

The Hip

  • Hip and thigh pain are common complaints in the ED [2].
  • Hip fractures have a very high one-year mortality [2].
  • Compared with CT, pelvic radiographs have a sensitivity of 64% to 78% for the identification of pelvic fractures in blunt trauma [3].
  • 2% of occult hip fractures will be missed by CT. Consider MRI for patients with significant hip pain and negative x-rays [2]. MRI hip protocols can be done in as little as 5-15 minutes.

Before we begin: Make sure to employ the rule of 2’s [4]

  • 2 views: One view is never enough
  • 2 abnormalities: If you see one abnormality, look for another
  • 2 joints: Image above and below the injury
  • 2 sides: If unsure regarding a potential pathologic finding, compare to another side
  • 2 occasions: Always compare with old x-rays if available
  • 2 visits: Bring patient back for repeat films

An approach to the traumatic adult hip x-ray

  1. Adequacy
  2. Bones
    • Inner Pelvic Ring
    • Obturator Foramina
    • Sacral Foramina
    • Outer Pelvic Ring
    • Acetabulum
      • Iliopectineal Line
      • Ilioischial Line
    • Femur
      • Shelton’s Line
  3. Cartilage/Joints
    • The SI Joint
    • Pubic Symphysis
  4. Consider an additional view

     1. Adequacy

    • A standard “hip series” consists of the AP view of the pelvis and a lateral view of the affected extremity.
      • There are multiple ways to perform the “lateral view”
      • For trauma: “Cross Table Lateral” or “Horizontal Beam Lateral” has these views
        • Require minimal movement of the affected painful hip
    • The AP radiograph of the pelvis should include the whole pelvis, proximal 3rd of the femur, and the lumbar spinous processes, coccyx, and pubic symphysis in a straight line [5].
      • The patient’s legs should be internally rotated to maximize visualization of the femur anatomy [6].
    • The lateral radiograph should include the acetabulum, ischial spine and tuberosity, and proximal femur.

Figure 1: Radiographic Normal AP Pelvis: Case courtesy of Dr. Jeremy Jones, Annotation by Stephen Villa, MD.

Figure 2: Radiographic Normal Cross Table Lateral: Acetabulum, Greater Trochanter, Lesser Trochanter, Ischial Tuberosity. Case courtesy of Andrew Murphy, Annotation by David Haase, MD.

     2. Bones

    • Examine the “Three rings“: Inner Pelvic Ring and 2 Obturator Foramina. They should be smooth. If disrupted, think fracture.
  • Figure 3: Inner Pelvic Rings. Case Courtesy of Dr. Jeremy Jones, Annotations by Stephen Villa, MD.


    • Arcuate Lines of Sacrum should be smooth and symmetrical.
  • Figure 4: Arcuate Lines of Sacrum. Case Courtesy of Dr. Jeremy Jones, Annotations by Stephen Villa, MD.


    • Outer Pelvic Ring
  • Figure 5: Outer Pelvic Ring. Case Courtesy of Dr. Jeremy Jones, Annotations by Stephen Villa, MD.

    • Acetabulum: Look for any cortical breaks
      • Ileopectinal Line: Disruption suggests fracture of the anterior column of the acetabulum
      • Ilioischial Line: Disruption suggest a fracture of the posterior column of the acetabulum
  • Figure 6: Acetabulum. Case Courtesy of Dr. Jeremy Jones, Annotations by Stephen Villa, MD.

    • Femur
      • Evaluate the femoral head, neck, intertrochanteric region (between greater and lesser trochanters), femoral shaft.
      • Shenton’s Line – Line from the medial femoral neck to the inferior edge of the superior pubic ramus, disruption is concerning for a femoral neck fracture.
Shenton's Line

Figure 7: Femoral anatomy and Shenton’s Line. Case courtesy of Dr. Jeremy Jones, Annotations by Stephen Villa, MD.


Figure 8: Cross Table Lateral. Case courtesy of Andrew Murphy,, Annotations by Stephen Villa, MD.

     3. Cartilage/Joints

    • The SI Joints: should be 2-4 mm.
    • Pubic Symphysis: should be <5 mm.

Figure 9: Case courtesy of Dr. Jeremy Jones,, annotations by Stephen Villa, MD.

     4. Consider an additional view

Frog Leg Lateral View

  • When: Because this view requires movement of the hips, it is not appropriate to obtain if concerned for fracture or dislocation. This view is used mostly in pediatrics.
  • Why: Helpful when concerned for Slipped Capital Femoral Epiphysis or Legg-Calve’-Perthes as it allows for better visualization of the femoral head.
Frog leg lateral pelvis xray

Figure 10: Frog leg lateral X-ray. Case courtesy of Dr. Ian Bickle,


“Pelvic Inlet/Outlet” View

  • When/Why: Do not perform when clinically concerned for fractures. The inlet view allows better visualization of the pelvic brim while the outlet view improves visualization of the SI joint/Sacral Foramina and the presence of vertical displacement.

Figure 11: A) Left – Inlet view. B) Right – Outlet view. Case courtesy of Andrew Murphy,


“Judet” View

  • When/Why: Allows for better visualization of acetabulum [7].

Figure 12: Judet view. Case courtesy of Dr. Luke Danaher,

Learn More

Want a more in-depth review? Check out Taming the Sru, Startradiology, or, all of which have excellent reviews of the pelvic x-ray.

Dealing with polytrauma? Check out EMRad’s approach to the wrist, foot, elbow, shoulder, ankle, or knee.


  1. Schiller P et al. Radiology Education in Medical School and Residency. The views and needs of program directors. Academic Radiology, Vol 25, No 10, October 2018. PMID: 29748056
  2. Stein M et al. Emergency Department Evaluation and treatment of Acute Hip pain. Emerg Med Clin N Am. Volume 33. Issue 2. May 2015. PMID: 25892725.
  3. Steele M, Norvell J. Chapter 269. Pelvis Injuries. In: Tintinalli’s Emergency Medicine. A Comprehensive Guide, 7th edition. New York: McGraw-Hill Education, 2011. P1841-1840
  4. Chan O. Introduction: ABCs and Rules of Two. ABC of Emergency Radiology, Third Edition. Edited by Otto Chan. 2013 John Wiley & Sons, Ltd. Published 2013.
  5. Sanville P et al. ABC of Emergency Radiology. The hip. BMJ. Volume 308. Feb 1994. PMID. 8136674
  6. Lim SJ et al. Plain Radiography of the Hip: A Review of Radiographic Techniques and Image Features. Hip Pelvis. Volume 27. Issue 3. Sep 2015. PMID 27536615.
  7. Hutt JR, Ortega-Briones A, Daurka JS et-al. The ongoing relevance of acetabular fracture classification. Bone Joint J. Volume 8. Aug 2015. PMID 26224834.



David Haase, MD

David Haase, MD

Department of Emergency Medicine
University of California, Los Angeles
Stephen Villa, MD

Stephen Villa, MD

Medical Education Fellow
Department of Emergency Medicine
University of California, Los Angeles