Why use a radial sequence for the hip labrum?

The acetabular labrum wraps around the joint as a curve. A radial acquisition takes slices that spoke out from the centre of the femoral head and so gives true perpendicular cross-sections of the labrum at every 'clock position'. A tear anywhere around the rim is then seen properly.

How does avascular necrosis appear on hip MRI?

As a serpiginous (snake-like) low-signal line beneath the articular surface on T1, often with bright bone-marrow oedema on STIR early on, before the subchondral bone collapses. That early window is when treatment still helps most.

Why internally rotate the feet for a hip MRI?

Gentle internal rotation profiles the femoral neck, so coronal and sagittal slices aligned to the neck axis show the head–neck junction and the weight-bearing surfaces in a standard, comparable way.

Hip MRI protocol (FAI and labrum)

A deep, curved joint where the labrum wraps a full circle and the femoral head is prone to avascular necrosis. The radial 'clock-face' sequence, spun around the femoral head, is what profiles the entire labrum.

By the ScanFlo Editorial Team · Updated 12 October 2026

In this section · Protocols

Protocols/Musculoskeletal

When this study is used

Femoroacetabular impingement (FAI) or labral tear.
Groin or hip pain, clicking or catching.
Suspected avascular necrosis of the femoral head.

Patient & coil positioning

Head-first supine; feet gently internally rotated and strapped to profile the femoral neck.
Torso/cardiac array for large-FOV survey, or a dedicated surface coil for high-resolution hip imaging.
Centre on the femoral head; pad for comfort, because hip patients in pain struggle to stay still.

Localizer

Three-plane localizer showing the whole femoral head, neck and acetabulum.

Sequence planning

For each sequence below you get the reference line the slice group follows, how much it covers, and why the sequence is in the protocol at all. Plan against the localizer, not by eye.

Coronal T1 + PD/T2 fat-sat

Coronal

Planning: Parallel to the femoral-neck axis on the axial.

Why: Bone anatomy and marrow (T1); bone-marrow oedema of impingement (fat-sat).

Radial PD fat-sat ('clock face')

Radial

Planning: 6–12 slices radiating from the centre of the femoral head like spokes on a wheel, on the axial.

Why: True perpendicular views of the entire acetabular labrum, so subtle tears are caught anywhere around the rim.

Sagittal / axial-oblique fat-sat

Sagittal / axial oblique

Planning: Perpendicular to the femoral neck (sagittal); axial oblique for the anterosuperior labrum.

Why: The anterosuperior labrum, the commonest impingement and tear site.

Coronal STIR

Coronal

Planning: Matched coverage.

Why: Early AVN oedema before subchondral collapse.

Representative parameters

Treat these as ranges. Field strength, coil and vendor all move the numbers. What must not move is understanding why each sits where it does.

Sequence	Field	Notes
Coronal T1	1.5–3 T	Anatomy, marrow, AVN line
Radial PD FS	1.5–3 T	6–12 spokes; whole labrum
STIR	1.5–3 T	Early AVN oedema
MR arthrogram T1 FS	1.5–3 T	If intra-articular contrast given

Artifacts & how to fix them

Artifact	Typical cause	Mitigation
Bowel / vessel motion	Nearby pelvic structures	Saturation bands; adequate coverage
Poor labral detail	Curved labrum not cut perpendicular	Radial sequence for true cross-sections
Metal blooming	Hip prosthesis	High bandwidth; TSE over GRE; MARS if available
Motion (pain)	Uncomfortable patient	Padding; shorten with parallel imaging

What am I looking at?

You are not reporting the study, but recognising pathology helps you keep it in the field of view and know when to add a sequence or contrast. How the common findings read on the console:

Finding	Sequence to check	How it reads
Labral tear	Radial / coronal PD FS	Bright signal into the labral substance or detaching it from the rim
Avascular necrosis	Coronal T1 + STIR	Serpiginous dark line on T1; bright marrow oedema early on STIR
FAI (cam/pincer)	Radial / axial oblique	Bony bump at the head–neck junction; marrow oedema

Review checklist

Coronal aligned to the femoral-neck axis.
Radial sequence covers the labrum around the whole clock face.
Anterosuperior labrum profiled on the oblique.
STIR reviewed for early AVN.

Mistakes that cost repeats

Relying on orthogonal planes that cut the curved labrum obliquely.
Missing early AVN by skipping a fat-sensitive sequence.
Femoral neck not profiled because of external rotation.
Motion from an uncomfortable, painful hip.

Common questions

Why use a radial sequence for the hip labrum?: The acetabular labrum wraps around the joint as a curve. A radial acquisition takes slices that spoke out from the centre of the femoral head and so gives true perpendicular cross-sections of the labrum at every 'clock position'. A tear anywhere around the rim is then seen properly.
How does avascular necrosis appear on hip MRI?: As a serpiginous (snake-like) low-signal line beneath the articular surface on T1, often with bright bone-marrow oedema on STIR early on, before the subchondral bone collapses. That early window is when treatment still helps most.
Why internally rotate the feet for a hip MRI?: Gentle internal rotation profiles the femoral neck, so coronal and sagittal slices aligned to the neck axis show the head–neck junction and the weight-bearing surfaces in a standard, comparable way.

Try it in ScanFlo: Plan a radial stack spoking out from the femoral head, then a standard coronal, and compare how the labrum is cut. The radial views show it in true cross-section all the way round. That is why subtle tears hide from orthogonal planes. See ScanFlo MRI →

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