Shoulder magnetic resonance imaging (MRI) in the sagittal plane is one of the most useful and frequently used orientations for evaluating shoulder pain and suspected soft-tissue injury. This guide explains sagittal shoulder MRI anatomy with a focus on normal findings, common variants, and how these images support accurate diagnosis. In the sagittal plane, the scanner slices the shoulder from front to back, providing a clear view of structures that run along the front-back axis. This overview is organized into major topics including the bony framework, articular cartilage, rotator cuff tendons, the long head of the biceps tendon, the labrum, capsular and ligamentous structures, and practical tips for reading sagittal shoulder MRI in clinical practice.
Normal Osseous Anatomy in Sagittal MRI
In sagittal MRI slices, the bony anatomy of the shoulder is clearly visible, including the humeral head, glenoid, and surrounding osseous structures. The humeral head appears as a rounded structure with homogeneous low signal on T1-weighted images and relatively higher signal on T2-weighted or fat-suppressed sequences. The articular cartilage covering the humeral head and glenoid should appear smooth, continuous, and of uniform thickness, signal intensity, and contour. The glenoid cavity itself is oriented roughly in the coronal plane, but in the sagittal plane you can assess its depth, the presence of osseous Bankart lesions, and the version of the glenoid. Bone marrow signal is typically low on T1 and intermediate on T2 unless fatty infiltration or edema is present. Recognizing these normal osseous features is essential to identify subtle fractures, bone contusion, or cystic changes at the articular margins.
Key Osseous Landmarks at a Glance
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Humeral head shape | Spherical to slightly elliptical in external rotation; more spherical in internal rotation | Anatomic imaging textbooks, cadaveric MRI studies |
| Glenoid orientation | Oval, slightly inclined in the scapular plane | MRI anatomy atlases, radiology literature |
| Articular cartilage thickness | Typically 1–2 mm on weight-bearing surfaces; varies by region | MR morphometry studies |
The Rotator Cuff in the Sagittal Plane
The rotator cuff tendons are assessed in multiple planes, with the sagittal plane particularly helpful for the supraspinatus and infraspinatus tendons. In sagittal images, the supraspinatus tendon inserts on the superior and mid humeral head, blending into the articular cartilage at the rotator cuff insertion. The infraspinatus tendon lies posteriorly and is best seen when the arm is positioned in internal rotation for some sequences. Tears of the supraspinatus often appear as tendon discontinuity, retraction, high-signal intensity on T2-weighted images, or fluid tracking into the subacromial-subdeltoid bursa. Longitudinal tears may be more clearly depicted in sagittal slices, whereas partial-thickness tears can be subtle and are better evaluated with careful attention to tendon thickness, fiber orientation, and signal intensity. Accurate diagnosis benefits from reviewing multiple sequences and planes to differentiate tendinopathy, partial tears, and full-thickness tears.
Recognition of Rotator Cuff Pathology on Sagittal MRI
- Tendon discontinuity or focal high-signal intensity extending to the articular surface
- Tendon retraction with mild to superior migration of the humeral head
- Intratendinous fluid or cystic changes at the insertion footprint
- Secondary signs such as subacromial bursal fluid or fat infiltration of the rotator cuff muscles
Long Head of the Biceps Tendon
The long head of the biceps tendon runs in the bicipital groove between the greater and lesser tuberosities and is well depicted in sagittal MRI slices. Normal tendon signal is typically low on T1- and T2-weighted images unless there is tendonosis, where high signal may be evident without distinct tears. Common sagittal findings include tendon thickening, mucoid degeneration, partial tears, and subluxation or dislocation of the tendon out of the bicipital groove. In the sagittal plane, you can evaluate the tendon’s course, its relationship to the surrounding tissues, and the presence of tenosynovitis or fluid within the tendon sheath.
Glenoid Labrum and Articular Cartilage
The glenoid labrum is a fibrocartilaginous rim that deepens the glenoid cavity and is critical for shoulder stability. In sagittal MRI, the labrum appears as a triangular or crescentic structure with intermediate to low signal on T1-weighted images and relatively higher signal on T2-weighted images. Labral tears, such as Bankart lesions or SLAP (superior labrum anterior to posterior) injuries, may show altered contour, abnormal signal, or contrast material extension into the labrum when contrast-enhanced sequences are used. The sagittal plane is especially useful for viewing the anterosuperior labrum and detecting labral bucket-handle tears or degenerative changes. Care must be taken to distinguish normal labral variants from true tears, as high signal within the labrum can be nonspecific and related to mucoid degeneration or surrounding edema.
Capsular, Ligamentous, and Periscapular Structures
Capsular and ligamentous structures around the glenohumeral joint are not always clearly visualized on MRI but contribute to joint stability. In sagittal sections, you can observe the inferior glenohumeral ligament complex, which is important for preventing inferior translation of the humeral head. An increase in capsular signal or joint distension with fluid suggests capsulitis or inflammatory synovitis. Periscapular muscles such as the teres minor and infraspinatus stabilizers surrounding the posterior structures can be evaluated. Fat-suppressed sequences help distinguish edema, inflammation, and reactive changes around the joint from normal fatty marrow. Repetitive overhead activities in athletes may show adaptive changes, whereas trauma may reveal capsular disruption or associated hematocele.
Practical Tips for Reading Sagittal Shoulder MRI
When interpreting sagittal shoulder MRI, systematically review osseous alignment, articular cartilage, rotator cuff tendons, the long head of the biceps tendon, and labral integrity. Compare T1-weighted and T2-weighted or STIR/fat-suppressed sequences to improve detection of edema, tears, and degenerative changes. Always correlate imaging findings with clinical history, physical examination, and, when appropriate, dynamic or contrast-enhanced sequences. Keep in mind that some high-signal intratendinous findings represent tendinosis rather than acute tears, and labral signal changes may be degenerative variants. Familiarity with common variants and artifacts reduces misinterpretation and supports accurate reporting. For complex or ambiguous cases, consider additional sequences or comparison with prior studies to establish a stable baseline.