Radiographic Procedures · ARRT Radiography
Femur, Pelvis & Hip
The 15-20 degree internal rotation rule, AP pelvis rotation checks, frog-leg contraindications, and the Danelius-Miller trauma hip lateral for the ARRT Radiography exam.
Overview
Femur, Pelvis and Hip runs on one anatomical fact: the femoral head and neck project 15 to 20 degrees anteriorly from the body of the femur. Rotate the whole lower limb internally 15 to 20 degrees and the neck lies parallel to the receptor; leave the feet vertical and the neck is partly foreshortened, with the lesser trochanter partly visible; full profile comes with external rotation. That single relationship sets the internal rotation for the AP hip, the AP pelvis and the proximal femur on the ARRT Radiography exam, where Procedures carries 66 of 200 scored questions to 28 February 2027 and 72 from 1 March 2027.
Three bones (ilium, ischium, pubis) fuse into one hip bone inside the acetabulum during the mid teens, and the female pubic arch runs 80 to 85 degrees against the male 50 to 60. The femoral neck is located 1 to 2 inches medial and 3 to 4 inches distal to the ASIS, and the neck-to-shaft angle averages about 125 degrees.
On the AP pelvis, the CR lands midway between the ASIS and the symphysis pubis, about 2 inches below the ASIS, and rotation is proved by symmetry of the iliac alae, ischial spines and obturator foramina. The frog-leg (modified Cleaves) abducts the femora 40 to 45 degrees but is forbidden with a possible fracture, dislocation, destructive hip disease or a hip replacement. The trauma lateral is the axiolateral inferosuperior Danelius-Miller method: CR perpendicular to the femoral neck, IR parallel to it, and the unaffected leg raised out of the beam.
Specials: Judet 45 degree obliques for the acetabulum, the AP axial inlet at 40 degrees caudad, and the Taylor outlet at 20 to 35 degrees cephalad for men or 30 to 45 for women. In suspected hip fracture an externally rotated foot is the classic sign, and the limb is never turned inward for a true AP.
What you’ll learn in this chapter
The 30 lessons in this chapter break down as follows. The full lesson content is unlocked when you start a free account.
Femur & Pelvis
- Femur, Pelvis & Hip
Anatomy
- The Proximal Femur
- Quiz
- Three Bones, One Hip Bone
- Landmarks You Palpate, Joints You Name
- True Pelvis, False Pelvis, Male, Female
- Quiz
Positioning
- Locating the Femoral Head and Neck
- Why the Limbs Turn In 15 to 20 Degrees
- Quiz
- Shielding, kV and the Upright Pelvis
Femur
- The Femur, AP and Lateral
- Splitting the Femur, and What Breaks
- Quiz
Pelvis
- AP Pelvis
- The Frog-Leg
- Quiz
- Inlet and Outlet
Acetabulum
- Obliques for the Acetabulum
Hip
- AP Unilateral Hip
- When the Leg Cannot Move
Critique
- Critiquing a Pelvis and a Hip
- Quiz
Clinical indications
- What You Are Being Asked to Show
Recap
- What to Carry Out of This Chapter
- Quiz
- Quiz
- Quiz
- Quiz
- Quiz
Key terms in this chapter
These are the 7 terms most likely to appear on the ARRT registry from this chapter. Use them as a flashcard pre-quiz.
- Femoral Neck Angle
- The head and neck project 15 to 20 degrees anteriorly from the body of the femur, which is why the whole lower limb is rotated internally 15 to 20 degrees for a true AP of the hip.
- Lesser Trochanter
- The rotation check on the AP pelvis, the AP hip and the Danelius-Miller lateral. In full profile medially it means the limb was externally rotated; invisible or barely visible means the internal rotation was correct.
- Danelius-Miller Method
- The axiolateral inferosuperior trauma lateral: CR perpendicular to the femoral neck, IR parallel to it, unaffected leg raised out of the beam. Used when the injured limb must not move.
- Modified Cleaves (Frog-Leg)
- The nontrauma hip lateral, with knees flexed about 90 degrees and femora abducted 40 to 45 degrees. Contraindicated with possible fracture, dislocation, destructive hip disease or hip replacement.
- Judet Method
- 45 degree posterior obliques of the acetabulum, taken right and left for comparison. Downside centering shows the anterior rim and posterior column; upside centering shows the posterior rim and anterior column with the obturator foramen open.
- Acetabulum
- The deep cup-shaped cavity where ilium, ischium and pubis meet and fuse during the mid teens. The ilium and ischium each form two fifths of it and the pubis one fifth.
- Taylor Method (Outlet)
- AP axial outlet projection angled 20 to 35 degrees cephalad for males and 30 to 45 degrees for females, the only projection in the chapter with sex-specific tube angles.
Sample practice question: Head, Spine, and Pelvis
One free sample from the 256-question Head, Spine, and Pelvis bank. See the format, the rationale style, and the difficulty before you sign up.
A 45° posterior oblique projection of the lumbar spine demonstrates the Scotty Dog pattern. A defect appearing as a 'collar' on the dog's neck represents which of the following pathologies?
Show answer and rationale
A, Incorrect: Spondylolisthesis is forward slippage of one vertebra on another, best assessed on lateral imaging.
B, Correct: Correct. The Scotty Dog's neck represents the pars interarticularis. A 'collar' on the neck indicates spondylolysis, a defect or fracture of the pars. This finding is pathognomonic on the 45° lumbar oblique.
C, Incorrect: Disk herniation is not directly visible on plain radiographs and requires MRI for diagnosis.
D, Incorrect: Compression fractures involve loss of vertebral body height and are best demonstrated on lateral views.
Hands-on
Practice the positioning
Open the Positioning Lab to drill body position, central ray, anatomy, and common errors for each projection in this chapter.
- AP Proximal Femur Supine, leg internally rotated 15-20 degrees. Hip joint included.
- AP Distal Femur Supine, leg extended in true AP. Knee joint included.
- Lateral Proximal Femur Lateral recumbent on affected side. Hip joint included.
- Lateral Distal Femur Lateral recumbent on affected side. Knee joint included.
- Hip AP Supine, legs extended and internally rotated 15-20 degrees. SID 40".
- Hip Lateral Supine, affected femur abducted 45 degrees with hip and knee flexed. SID 40".
- Hip Axiolateral Supine, affected leg extended, opposite leg raised out of the field. Horizontal cross-table CR. SID 40".
- Pelvis AP Supine, legs extended and internally rotated 15-20 degrees. SID 40".
- Femoral Neck AP Oblique (Modified Cleaves) Supine, hips and knees flexed about 90 degrees, femora abducted 40-45 degrees, soles together. SID 40".
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Frequently asked questions
What does the ARRT Radiography Radiographic Procedures category cover?
Femur, Pelvis and Hip runs on one anatomical fact: the femoral head and neck project 15 to 20 degrees anteriorly from the body of the femur. Rotate the whole lower limb internally 15 to 20 degrees and the neck lies parallel to the receptor; leave the feet vertical and the neck is partly foreshortened, with the lesser trochanter partly visible; full profile comes with external rotation. That single relationship sets the internal rotation for the AP hip, the AP pelvis and the proximal femur on the ARRT Radiography exam, where Procedures carries 66 of 200 scored questions to 28 February 2027 and 72 from 1 March 2027.
How many lessons are in the Femur, Pelvis & Hip chapter?
This chapter contains 30 lessons across 10 sections, plus a knowledge-check quiz at the end. The full lesson content is unlocked with a Premium subscription. The free tier includes 3 complete chapters.
Is this chapter aligned with the current ARRT Content Specifications?
Yes. Every chapter on this site maps directly to the ARRT Radiography Content Specifications in effect for your exam window. This chapter falls under the Radiographic Procedures domain of the official ARRT exam blueprint.