MRI of Hip Labral and Capsulolabral Lesions
A practical radiology review of MRI of Hip Labral and Capsulolabral Lesions, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.
A practical radiology review of MRI of Hip Labral and Capsulolabral Lesions, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.
- Why Important?
- Labrum = stability + suction seal + load distribution
- Key in FAI → early OA pathway
- Common cause of groin pain + clicking + ↓ ROM
Anatomy Essentials
- Labrum = fibrocartilage rim (triangular )
Attachments
- Osseolabral
- Chondrolabral (tidemark)
- Poor vascularity → poor healing
Stabilizers Trio
- Labrum
- Capsule + ligaments (iliofemoral, etc.)
- Ligamentum teres (secondary stabilizer)
Localization
- Clock-face system
- 3 o’clock = anterior
- 12 = superior
- 6 = transverse ligament
Most tears: anterosuperior quadrant
Pathophysiology (FAI)
- Cam → femoral head-neck bump
- Pincer → acetabular overcoverage
- Result: shear stress → chondrolabral separation, cartilage damage → OA
MRI Technique
- Best modality
- Direct MR Arthrography (MRA)
- ↑ joint distension
- ↑ contrast resolution
- ↑ sensitivity for labral tears
- Current trend; 3T MRI:sensitivity ~ MRA
- higher specificity in some studies
- Key technical tips: Small FOV (14–18 cm)
- Radial imaging → ↓ partial volume
- Thin cartilage = detection difficult
- MRI struggles with cartilage
Labral Pathology
Types
- Degeneration → ↑ signal, no surface breach
Tear
- Substance tear
- Partial detachment
- Complete detachment
- Complex tear
- Mechanism
- Starts at chondrolabral junction
Progression
- separation → detachment → full tear
Key MRI Findings
- Linear signal reaching surface = tear
- Fluid undermining base = detachment
- Paralabral cyst → strong tear indicator (~94%)
Normal Variants
- Sublabral sulcus smooth margins, <50% width fluid, no adjacent pathology, Paralabral recess,Transverse ligament recess
Differentiation from tear
- Tear = irregular + extends into labrum
- Variant = smooth + linear
- Chondral Lesions-->Often with labral tears
- Difficult detection (thin cartilage)
Special lesion
- Carpet lesion (delamination) → classic in cam FAI
Postoperative Imaging
Normal postop
- Smaller labrum
- Smooth margins
- Paralabral recess often obliterated
Retear signs
- Fluid signal reaching surface
- New extension beyond repair zone
- Paralabral cyst
- Labral distortion
Pitfall
- Postop ↑ signal ≠ always retear (granulation tissue)
- Capsule & Ligamentum Teres
- Capsule: injury → instability
- postop → dehiscence = fluid gap
Ligamentum teres
- rotational stability
- tears → seen better on MRA
- Ultra High-Yield Pearls
- MRA = best for labrum (classic exam answer)
- 3T MRI ≈ MRA (modern practice nuance)
- Most tears = anterosuperior
- Always rule out normal variants
- Paralabral cyst = tear until proven otherwise
- Carpet lesion = cam impingement clue
- Cartilage evaluation = weak point of MRI
Clinical use note
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