Centering points & palpable references
Spherical proximal humerus articulating with the glenoid.
Why it matters: Centering landmark for shoulder AP; rotation determines greater vs lesser tubercle profile.
Posterior projection of the proximal ulna forming the elbow tip.
Why it matters: Palpable centering point for elbow lateral; superimposes humeral epicondyles on true lateral.
Lateral projection of the distal radius — palpable at the thumb-side wrist.
Why it matters: Should project at the same level as the ulnar styloid on a true PA wrist.
Medial projection of the distal ulna.
Why it matters: Profiles in the back of a true lateral wrist; superimposes radius on a perfect lateral.
Most lateral proximal-row carpal — most commonly fractured carpal.
Why it matters: Ulnar deviation PA elongates the scaphoid and opens the waist for fracture detection.
Crescent-shaped second carpal of the proximal row.
Why it matters: 'Pie sign' on lateral indicates dislocation. Sits centrally between scaphoid and triquetrum.
Articulation between the 3rd metacarpal head and proximal phalanx.
Why it matters: Centering point for PA and oblique hand.
Lateral bony prominence at the proximal femur — easily palpable on the lateral hip.
Why it matters: Centering reference for AP hip and AP pelvis; midline lies 1 in (2.5 cm) medial.
Sesamoid bone within the quadriceps tendon.
Why it matters: Centered over the femur on a true AP knee with leg internally rotated 3–5°.
Superior articular surface of the tibia.
Why it matters: Knee joint opens when CR enters ½ in below the patellar apex with 0–5° cephalad angle.
Distal projection of the tibia.
Why it matters: True AP closes mortise; 15–20° internal rotation opens it. Centering point for ankle AP.
Distal projection of the fibula — sits more posterior than the medial malleolus.
Why it matters: Plantar-flexion + 15–20° internal rotation profiles it on mortise view.
Bears all body weight transmitted from the tibia.
Why it matters: All four mortise spaces should appear open on the AP-mortise view.
Largest of the tarsals; forms the heel.
Why it matters: Axial (plantodorsal) projection requires 40° cephalic CR for sustentaculum tali profile.
Inferior tip of the mastoid process, just posterior to the ear.
Why it matters: Centering landmark for AP open-mouth (C1–C2) — center 1 in below mastoid tips.
Surface landmark for C4–C5 disc space.
Why it matters: Centering point for AP and lateral cervical spine.
Most prominent spinous process at the cervicothoracic junction.
Why it matters: MUST be visible on lateral C-spine; if obscured by shoulders, perform a Swimmer's projection.
Suprasternal notch at the superior border of the manubrium (~T2–T3).
Why it matters: Centering landmark for AP shoulder, sternum, and approximate level of T2/T3.
Inferior cartilaginous tip of the sternum (~T9–T10).
Why it matters: Marks the level of T9/T10 — useful boundary for AP thoracic spine centering.
Superior margin of the ilium — palpable laterally at the waist.
Why it matters: Reliable surface landmark for L4–L5 interspace; centering point for AP lumbar spine.
Anterior Superior Iliac Spine — palpable bony prominence at the front of the pelvis.
Why it matters: Centering reference for AP pelvis (2 in inferior) and SI joints.
Suprasternal notch at the top of the manubrium (~T2–T3).
Why it matters: Top of IR for PA chest sits ~1.5 in above the shoulders so apices are included.
Most prominent posterior cervical spinous process.
Why it matters: Top-of-IR landmark for PA chest from the back — IR 1.5–2 in above C7.
Mid-thoracic vertebra — approximately at the inferior scapular angle.
Why it matters: PA chest centering — CR perpendicular to T7 (7–8 in below vertebra prominens).
Cartilaginous tip of the sternum at ~T9–T10.
Why it matters: Inferior boundary reference; AP ribs above-diaphragm centers between jugular notch and xiphoid.
Lateral angles where ribs meet diaphragm.
Why it matters: Must be sharp and included on every PA chest — clipping = repeat.
Bifurcation of the trachea into the main-stem bronchi (~T4–T5).
Why it matters: Reference for ET tube placement and central line tip evaluation.
Superior margin of the ilium — palpable at the waist.
Why it matters: Top-of-IR landmark for AP pelvis; correlates with L4–L5.
Anterior Superior Iliac Spine — bony prominence at front of pelvis.
Why it matters: Center 2 in (5 cm) inferior for AP pelvis; midway between ASIS and symphysis for AP hip.
Lateral femoral prominence — palpable on the lateral hip.
Why it matters: Same level as the superior border of the symphysis; centering reference for hip and pelvis.
Cartilaginous joint between the two pubic bones.
Why it matters: Inferior landmark for AP pelvis; must be included with no clipping.
Connects the femoral head to the shaft; common fracture site in elderly.
Why it matters: Profiled with 15–20° internal rotation of the leg — lesser trochanter should not be visible.
Large opening bounded by ischium and pubis.
Why it matters: Symmetry confirms a non-rotated AP pelvis.
Smooth prominence between the eyebrows.
Why it matters: Centering point for AP axial (Towne) — CR enters glabella with 30° caudal angulation.
Depression at the bridge of the nose where frontal and nasal bones meet.
Why it matters: Centering reference for PA skull and Caldwell projections.
Junction of the nose and upper lip.
Why it matters: Centering point for the Waters projection of the facial bones / maxillary sinuses.
Most anterior point of the chin.
Why it matters: Used to define the mentomeatal line (MML) for the Waters projection (perpendicular to IR).
Opening of the external auditory canal.
Why it matters: Reference for positioning lines (OML connects outer canthus to EAM); centering for AP/PA axial skull and SMV.
Lateral corner of the eye.
Why it matters: Used to define the OML (outer canthus → EAM) — the foundation of skull positioning.
Where the auricle meets the side of the head.
Why it matters: Centering landmark for AP axial Towne (2 in superior); approximates the level of the EAM.