Hip labral tear is a partial or complete detachment of the acetabular labrum — the fibrocartilaginous ring structure surrounding the acetabular rim. Femoroacetabular impingement (FAI) is the most common etiological factor: cam-type (bony protuberance at the femoral head-neck junction) and/or pincer-type (acetabular over-coverage) morphology causes mechanical damage to the labrum. The anterior-superior labrum is the most commonly torn location (70-90%). It is common in young active adults and athletes. MR arthrography (MRA) is the gold standard for diagnosis, with contrast material leaking through the labral tear being diagnostic. Paralabral cysts may accompany and serve as indirect evidence of labral pathology. Untreated labral tears contribute to the development of osteoarthritis.
Age Range
20-55
Peak Age
35
Gender
Equal
Prevalence
Common
The acetabular labrum is a triangular cross-section ring structure composed of a mixture of hyaline and fibrous cartilage that attaches to the acetabular rim. The labrum has three fundamental functions: (1) enhancing joint stability — labrum removal reduces femoral head coverage by 22%, (2) maintaining intra-articular negative pressure (suction seal) — the labrum's sealing function optimizes nutrient diffusion to articular cartilage, (3) peripheral joint fluid sealing — cartilage-protective mechanism. In FAI, cam morphology (alpha angle >55°) causes the non-spherical portion of the femoral head to impinge on the labrum during flexion and internal rotation → repetitive mechanical trauma → labral detachment. In pincer morphology (lateral center-edge angle >40°), acetabular over-coverage compresses the labrum → crush injury. Paralabral cyst formation at the tear site is explained by synovial fluid leaking from the labral defect into the perilabral area — a one-way valve mechanism (fluid exits but cannot return) leads to cyst growth. On MRA, when contrast leaks through the labral tear, contrast accumulation (imbibition) is seen between the labrum and acetabulum — this is direct evidence of the tear.
On MR arthrography, gadolinium-based contrast material leaking through the tear at the labrum-acetabulum junction, creating linear high signal within the labral substance or beneath the labrum. This is the most direct and reliable evidence of labral tear. Contrast leak allows determination of tear location, size, and type (partial/complete).
On MR arthrography (MRA) T1 fat-sat images, gadolinium-based contrast material leaks through the tear at the labrum-acetabulum junction and appears as linear high signal within the labral substance or between the labrum and acetabular cartilage. This is direct evidence of labral tear. MRA has 92-95% sensitivity and 91-93% specificity for labral tear detection. The contrast leak also allows assessment of whether the tear is full-thickness or partial-thickness.
Report Sentence
Contrast material leak is seen at the anterior-superior labrum on MR arthrography, consistent with a labral tear.
On T2-weighted and STIR images, a well-defined, markedly hyperintense cystic lesion is seen adjacent to the labrum. Paralabral cysts are indirect but highly reliable evidence of labral tear — the probability of labral tear in the presence of a paralabral cyst is >90%. Cyst size can range from a few mm to 2-3 cm. The cyst is usually adjacent to the tear site and a stalk-like connection can be demonstrated showing it is fed from the tear.
Report Sentence
A T2 hyperintense paralabral cyst is seen adjacent to the anterior-superior labrum, suggesting underlying labral tear.
On axial oblique MRI images (parallel to femoral neck axis), the alpha angle is measured at the femoral head-neck junction. Normal alpha angle is <55°; >55° is defined as cam morphology. The cam lesion appears as a bony protuberance ('bump') at the femoral head-neck junction — this bump impinges on the anterior-superior labrum during flexion and internal rotation. MRI provides better soft tissue contrast than CT and evaluates both bony morphology and labral damage simultaneously.
Report Sentence
The alpha angle is elevated (>55°) at the femoral head-neck junction on axial oblique images, consistent with cam-type femoroacetabular impingement morphology.
On conventional (non-arthrographic) MRI, the torn labrum shows intralabral signal increase, labral morphologic disruption (blunting, irregularity, thinning), or labral separation (detachment) on T2-weighted images. Normal labrum shows homogeneous low signal (fibrocartilage). In the tear area, local T2 signal increase is seen due to synovial fluid infiltration. Conventional MRI sensitivity is lower than MRA (66-75% vs 92-95%) but has the advantage of being non-invasive.
Report Sentence
T2 signal increase and morphologic disruption are noted in the anterior-superior labrum, consistent with labral tear.
CT is superior to MRI for evaluating bony morphology. On axial and oblique sagittal reformats, the cam lesion (bony protuberance at the femoral head-neck junction) and alpha angle measurement can be performed. 3D CT reconstruction is the gold standard for FAI surgical planning — cam resection volume and pincer trim area are determined. Assessment of acetabular retroversion (crossover sign) and protrusio acetabuli in pincer morphology is more definitive with CT.
Report Sentence
A bony protuberance consistent with cam morphology (alpha angle >55°) is seen at the femoral head-neck junction on CT.
Criteria
Labral tear with alpha angle >55°. Common in young male athletes. The non-spherical portion of the femoral head impacts the labrum-cartilage junction during flexion.
Distinct Features
Labral tear typically in anterior-superior location. Accompanying acetabular cartilage damage is common — 'outside-in' damage mechanism (labrum → cartilage delamination). Cartilage-labral separation may be more prominent than labral detachment.
Criteria
Labral tear with LCE angle >40° or acetabular retroversion (crossover sign). More common in middle-aged women.
Distinct Features
Labral 'crush' injury — labrum is compressed between acetabulum and femoral head. Labral degeneration and ossification are common. Contralateral (posteroinferior) cartilage damage ('contre-coup'). Labral tear is typically anterior but unlike cam, cartilage damage is peripheral and limited.
Criteria
Tear developing from age-related labral degeneration without FAI morphology. Usually >50 years old. Associated with osteoarthritis.
Distinct Features
Labrum is diffusely degenerative — signal increase and morphologic disruption are widespread. Accompanying osteophytes, joint space narrowing, and subchondral changes. Paralabral cyst is less common because the tear is typically complex and multidirectional.
Distinguishing Feature
AVN shows pathognomonic double-line sign in femoral head on T2 and subchondral bone involvement without labral pathology, while labral tear shows labrum-cartilage junction pathology with normal femoral head marrow
Distinguishing Feature
Transient osteoporosis shows diffuse bone marrow edema in femoral head (hyperintense on STIR) without subchondral changes, while labral tear has no marrow edema and labral morphologic disruption is predominant
Distinguishing Feature
Isolated ganglion cyst can occur without labral tear but perilabral ganglion cyst is strongly associated with labral pathology; stalk connection between cyst and labrum suggests tear
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralLabral tear treatment is determined by symptom severity, patient activity level, and accompanying pathology. Conservative treatment (physical therapy, NSAIDs, activity modification) is tried initially. If unsuccessful, arthroscopic labral repair or debridement is performed. If FAI morphology is present, simultaneous cam resection (osteoplasty) and/or pincer trim is performed — otherwise the tear recurs. Referral to a hip preservation surgery specialist is recommended. Untreated labral tears contribute to early osteoarthritis development.
Labral tears cause groin pain and restricted motion. Combined with FAI, they increase the risk of early osteoarthritis. Arthroscopic labral repair or debridement is performed for symptomatic tears. Surgical correction of FAI morphology (osteoplasty) should be performed together with tear repair.