The glenoid labrum is the fibrous attachment of the glenohumeral ligaments and capsule to the glenoid rim. The labrum is ovoid, conforming to the essentially kidney-shaped glenoid rim. The normal glenoid labrum is 3 mm high and 4 mm wide, but its size, shape, and configuration vary considerably, both between individuals, from side to side in the same individual, and with changes in the position of the humeral head.

The anterior glenoid labrum provides the major area of attachment for the anterior band of the inferior glenohumeral ligament. The middle glenohumeral ligament is considerably more variable, but may also contribute fibers to the more superior aspects of the anterior glenoid labrum as it approaches the biceps tendon.

Above the epiphyseal line (i.e., the junction of the upper and middle one-thirds of the glenoid body fossa), the attachment of the glenoid labrum is variable. The superior labrum does have a role in the stability of the glenohumeral joint and functions in conjunction with the biceps tendon, with which it is contiguous (the biceps labral complex). Inferior to the epiphyseal line the labrum is continuous with the glenoid articular cartilage and serves as the insertion site for the inferior glenohumeral ligament.

The superior and anterosuperior portion of the labrum can be variably attached to the glenoid. There are three different types of attachment of the biceps labral complex (BLC) to the glenoid:

Type 1 : The BLC is firmly adherent to the superior pole of the glenoid and there is no sublabral foramen in the anterosuperior quadrant.

Type 2 : The BLC is attached several millimeters medial to the sagittal plane of the glenoid. The superior pole of the glenoid continues its hyaline cartilage surface medially under the labrum. In this configuration there is a small sulcus at the anterosuperior quadrant that communicates with the subscapularis bursa and may be associated with a sublabral foramen.

Type 3 : In type 3 BLC the labrum is very meniscoid in shape and there is a large sulcus that projects under the labrum and over the cartilaginous pole of the glenoid. The type 3 BLC attaches primarily to the supraglenoid tubercle, creating a synovial lined sulcus at the superior aspect of the glenoid. This normal sulcus should not be mistaken for a superior-labral-anterior-to-posterior (SLAP) lesion or a sublabral foramen.