Hip Labral Tear MRI Signs: FAI, MR Arthrogram, and Paralabral Cysts

MR arthrogram (MRA) involves intra-articular injection of dilute gadolinium contrast under fluoroscopic guidance, followed by MRI. The gadolinium distends the joint capsule and infiltrates labral tears, producing high signal against the normally dark fibrocartilaginous labrum on fat-suppressed T1-weighted sequences. MRA raises the sensitivity for labral tears from approximately 30–60% on conventional MRI to 87–95%, with comparable improvements in specificity. The technique also delineates paralabral cysts, cartilage undermining at the chondrolabral junction, and the location of the tear around the acetabular clock face, information that guides arthroscopic repair planning.

Radial reformats are oblique MRI sequences acquired in a series of planes oriented radially around the femoral neck, typically at 8 to 12 positions spanning the full circumference. Each reformat is perpendicular to the femoral neck axis at a given clock-face position, providing an orthogonal view of the head-neck junction and adjacent labrum at that location. This approach eliminates the partial-volume averaging that degrades standard axial and coronal images at the anterior and posterior margins of the hip. Radial reformats allow precise alpha angle measurement at the site of maximum cam deformity and improve detection of anterosuperior labral tears and associated cartilage delamination — pathology frequently missed on conventional MRA planes alone.

MRI can show labral signal abnormality, detachment, paralabral cysts, adjacent cartilage injury, and indirect signs of impingement. MR arthrogram can make some tears more conspicuous because contrast enters the tear plane. Imaging still needs clinician review alongside symptoms, examination, and prior treatment history.

X-ray and CT generally do not visualize the acetabular labrum directly. They are still useful because they show the bony drivers that often accompany labral injury: cam-type femoral head-neck offset, pincer overcoverage, acetabular dysplasia, version abnormalities, arthritis, or subtle fracture. MRI or MR arthrogram is needed when the clinical question is the labrum, cartilage, paralabral cysts, or fluid tracking into a tear.

CT is better for three-dimensional bony morphology, version, cortical fracture detail, and surgical planning around cam or pincer correction. MRI is better for the labrum, cartilage, marrow edema, and soft tissues. CT should complement the clinical and MRI picture rather than replace it for labral questions.

A clinician should confirm that symptoms fit an intra-articular hip source, review range of motion and provocative tests, evaluate FAI or dysplasia, assess cartilage status, and decide whether the imaging finding is incidental or likely responsible for the patient's pain. Imaging alone cannot prove symptom causation.

AI cannot determine whether a tear is the true pain generator, decide if arthroscopy is appropriate, judge hip stability, or replace a radiologist, sports medicine clinician, or hip surgeon. It can summarize visible imaging patterns for discussion with a clinician, but it is not a diagnosis or treatment plan.

Small, stable labral tears without associated FAI morphology may become asymptomatic with conservative management — targeted physical therapy to improve hip rotator strength and neuromuscular control, activity modification, and intra-articular corticosteroid or platelet-rich plasma injections. However, the labrum has limited intrinsic healing capacity due to its largely avascular fibrocartilaginous composition, particularly in the inner two-thirds. Tears associated with cam or pincer impingement are subject to ongoing mechanical stress and rarely resolve without addressing the underlying bony morphology. Arthroscopic labral repair, combined with cam resection or acetabuloplasty when indicated, restores biomechanical function and achieves good-to-excellent outcomes in appropriately selected patients.