How To Read A Mri Of The Shoulder

You're staring at a series of grayscale slices. And coronal, sagittal, axial. T1, T2, PD, STIR. The patient's name is at the top. And the history says "chronic shoulder pain, ? rotator cuff tear." And you're thinking: where do I even start?

I've been there. We all have. Now, the first time you open a shoulder MRI on your own — no attending leaning over your shoulder, no resident to whisper "check the supraspinatus" — it feels like reading a map without a legend. But here's the thing: shoulder MRI isn't magic. It's anatomy you already know, just sliced differently. And once you build a routine, it stops being overwhelming Easy to understand, harder to ignore. But it adds up..

Let's walk through it the way I wish someone had walked me through it.

What Is a Shoulder MRI

Magnetic resonance imaging of the shoulder uses strong magnetic fields and radiofrequency pulses to generate detailed images of soft tissue and bone. Day to day, no radiation. No contrast required for most routine studies — though MR arthrography (injecting gadolinium into the joint) adds sensitivity for labral tears and partial-thickness cuff tears.

The standard protocol gives you three planes: coronal oblique (perpendicular to the supraspinatus tendon), sagittal oblique (parallel to it), and axial. Sagittal shows the biceps anchor and posterior labrum beautifully. On the flip side, each plane has a job. Coronal shows the rotator cuff tendons end-to-end. Axial catches the subscapularis and the glenohumeral ligaments.

You'll see sequences weighted for different tissue properties. Also, that's where you hunt for edema, tears, inflammation. Great for anatomy, marrow signal, chronic changes. Plus, t1-weighted images — fat is bright, fluid is dark. That said, t2-weighted and proton density (PD) — fluid is bright. Fat-suppressed versions (STIR, SPAIR, FS-PD) null out fat so fluid screams at you That's the whole idea..

The Planes Aren't Optional

Skip one plane and you'll miss something. Even so, i've seen experienced radiologists miss a subscapularis tear because they only looked at coronals. The axial plane exists for a reason. Use it That's the part that actually makes a difference..

Why It Matters

Shoulder pain is the third most common musculoskeletal complaint in primary care. MRI is the gold standard for surgical planning — but only if the read is accurate. Consider this: a missed partial-thickness articular surface tear means a patient gets PT for six months when they needed a scope. An overcalled SLAP lesion means unnecessary surgery on a 55-year-old with degenerative fraying.

It sounds simple, but the gap is usually here.

And here's what most people miss: the report drives the referral. Orthopedic surgeons trust specific language. Which means "High-grade partial tear >50% thickness" gets a different conversation than "partial tear. " "Displaced bucket-handle tear of the posterior labrum" gets the patient on the schedule. "Labral signal" gets a shrug.

No fluff here — just what actually works.

Your words change management. That's the job.

How to Read It — A Repeatable System

Don't freestyle. Build a checklist and run it every single time. Here's mine.

1. Start With the Bones

Before you touch a tendon, scroll through the marrow. T1 and STIR side by side.

Look for:

• Fractures (acute lines, edema)
• Osteonecrosis (humeral head — think sickle cell, steroids, trauma)
• Arthritis (subchondral cysts, sclerosis, cartilage loss)
• Tumors (rare but real — don't be the one who misses a metastases)
• Hill-Sachs and bony Bankart lesions (posterior humeral head impression fracture, anterior glenoid rim fracture — instability markers)

Degenerative changes at the acromioclavicular joint? Here's the thing — common. Only mention if symptomatic or causing impingement.

2. Rotator Cuff — The Main Event

Four tendons. Four distinct failure patterns. Know them.

Supraspinatus — the usual suspect. Coronal oblique is your primary plane. Track it from muscle belly to footprint on the greater tuberosity. Normal tendon: uniform low signal, smooth contours, inserts broadly on the footprint.

Tears:

• Full thickness: fluid signal cleaves the tendon top to bottom. Articular surface (PASTA lesion) — look for fluid tracking into the tendon from the joint side. Which means retraction? Intrasubstance — fluid entirely within tendon substance. Medial to the glenoid = massive. Measure it. Bursal surface — fluid on the subacromial side. Grade by thickness: <25% low grade, 25-50% moderate, >50% high grade. - Partial thickness: trickier. Muscle atrophy and fatty infiltration (Goutallier grading) on sagittal T1 tell you chronicity and repairability. At the footprint = small. High-grade partials often behave like full-thickness tears surgically.

Counterintuitive, but true.

Infraspinatus — posterior cuff. Tears here mean external rotation weakness. Often extend from supraspinatus tears. Check the sagittals for muscle quality Less friction, more output..

Subscapularis — anterior. Axial plane is non-negotiable. Look at the tendon fibers inserting on the lesser tuberosity. Tears: partial (upper third most common), full thickness, or "rolled" retracted stump. Biceps subluxation? Check the bicipital groove — if the subscap is torn, the biceps can medially dislocate. That's a surgical detail.

Teres minor — rare isolated tears. But if it's atrophied with a normal tendon, think quadrilateral space syndrome or nerve injury Most people skip this — try not to..

3. The Biceps Tendon — Long Head

Originates at the supraglenoid tubercle and superior labrum. Runs in the bicipital groove, held by the transverse humeral ligament (really the subscapularis and supraspinatus forming a sling) And that's really what it comes down to..

Check:

• Tendinosis: thickened, intermediate signal on T1/T2
• Partial tear: fluid signal within, thinning
• Full tear: empty groove, retracted muscle belly ("Popeye" sign)
• Subluxation/dislocation: medial (subscap tear) or lateral (rare)
• SLAP involvement: the anchor is the superior labrum. If the biceps anchor is peeled, that's a SLAP lesion — more on that in a minute.

4. Labrum — The Ring That Matters

Glenoid labrum deepens the socket. Because of that, normal: low signal triangle on all sequences. But — and this is critical — the anterosuperior labrum (11 o'clock to 1 o'clock) can have a normal sublabral foramen or Buford complex (absent anterosuperior labrum with cord-like middle glenohumeral ligament). Don't overcall a tear here.

Some disagree here. Fair enough.

SLAP lesions (Superior Labrum Anterior to Posterior):

• Type I: fraying, no detachment. Often asymptomatic. The "peeled" appearance. Look for fluid under the superior labrum on coronal and sagittal. The surgical one. - Type III: bucket-handle tear of superior labrum, biceps anchor intact. Degenerative. - Type II: biceps anchor detached from glenoid. - Type IV: bucket-handle extends into biceps tendon.

It sounds simple, but the gap is usually here Not complicated — just consistent..

Posterior labral tears: common in posterior instability, internal impingement (throwers). Look on sagittals and axials. Kim lesion (post

5. The Remaining Cuff‑Related Structures

While the supraspinatus, infraspinatus, and subscapularis dominate the cuff‑repair discussion, a few ancillary tendons deserve equal attention on the MRI report Still holds up..

• Coracobrachialis – Originates from the coracoid process and inserts on the humeral shaft. On sagittal T1‑weighted images it appears as a thin, low‑signal strap. Hypertrophy or tendinopathy is uncommon, but when present it may mimic a subtle rotator‑cuff tear if the surrounding cuff edema is misinterpreted. Coracobrachialis lesions are usually focal and should be described as “isolated coracobrachialis tendinopathy” unless a clear tear is evident.

• Pectoralis Major (clavicular head) – Though not part of the classic cuff, its insertion on the humeral head can be involved in massive rotator‑cuff tears, especially when the tendon is retracted superiorly. On axial images the tendon appears as a triangular low‑signal structure anterior to the glenoid. A tear will show a discontinuity with surrounding edema and may be associated with a “pseudoglenoid” appearance Most people skip this — try not to..

• Long Head of Biceps (LHB) – Accessory Portions – The LHB may give off small slips to the glenoid labrum or to the capsule. These slips can develop partial tears that are easily overlooked on standard sequences. High‑resolution 3‑D GRE or CISS sequences are useful for delineating these tiny fibers. When a slip is torn, contrast‑enhanced MR‑arthrography can demonstrate a persistent connection to the labrum, helping to differentiate a true SLAP lesion from an isolated biceps tendon tear Small thing, real impact. And it works..

6. Muscle Quality and Fat Infiltration

Beyond structural tears, the chronicity of a rotator‑cuff lesion is best reflected by the fatty infiltration of the involved muscles. On T1‑weighted images, normal muscle appears isointense, whereas fatty tissue is hyperintense. The “Goutallier classification” (Stage 0‑4) provides a semi‑quantitative assessment:

Short version: it depends. Long version — keep reading.

• Stage 0 – No visible fat
• Stage 1 – Equivalent to normal subcutaneous fat
• Stage 2 – More fat than normal
• Stage 3 – Marked fat, muscle fibers still discernible
• Stage 4 – Nearly complete fatty replacement, only remnants of muscle remain

When a chronic tear is identified, documenting the stage of fatty infiltration is essential for surgical counseling. High‑grade infiltration (Stage 3‑4) often predicts poorer functional recovery after repair, even when the tear is anatomically reducible.

7. Associated Pathology

• Subacromial‑Bursitis – Fluid collections in the subacromial recess are best seen on T2‑weighted or PD‑weighted sequences. A “bursal effusion” that tracks anteriorly may indicate an underlying rotator‑cuff tear, especially when the fluid extends into the tendon substance (intra‑tendinous fluid sign). In chronic cases, a thickened bursa may appear as a well‑defined, intermediate‑signal structure with peripheral enhancement after contrast.

• Glenohumeral Joint Effusion – A moderate joint effusion can be an indirect sign of intra‑articular pathology such as SLAP lesions or chondral injury. On sagittal T1‑weighted images, a normal joint space is approximately 2–3 mm; effusions widen this space and may produce a “meniscus‑like” low‑signal rim representing compressed synovium.

• Cartilage Degeneration – The glenoid cartilage is best visualized on high‑resolution PD‑FS or 3‑D GRE sequences. Focal cartilage loss appears as a focal absence of the normally low‑signal cartilage with adjacent subchondral bone edema. In massive rotator‑cuff tears, chronic superior migration of the humeral head can lead to “reverse Hill‑Sachs” lesions on the humeral head surface, which are best appreciated on axial T1‑weighted images.

8. Reporting Tips for the Radiologist

1. Use Consistent Anatomic Landmarks – Reference the “12‑o’clock” position of the glenoid when describing labral lesions; this eliminates ambiguity when comparing studies over time.

2. Describe Both Morphology and Signal Characteristics – Rather than simply stating “tear present,” specify the type (partial vs. full‑thickness), location (e.g., “posterior supraspinatus tendon involving the infraspinatus footprint”), and signal behavior (e.g., “fluid‑filled defect with peripheral enhancement”) Not complicated — just consistent..

3. Correlate With Clinical Context – A small, low‑grade partial tear in an asymptomatic athlete may be managed conservatively, whereas the

whereas the chronic, high‑grade fatty infiltration (Stage 3‑4) may necessitate more aggressive surgical debridement and can blunt the likelihood of functional restoration, even when the tear is reducible Easy to understand, harder to ignore. Practical, not theoretical..

Additional reporting recommendations

4. Assess tendon retraction – Measure the distance the distal tendon has pulled from its anatomic footprint, using the “J‑sign” or “crescent‑sign” on coronal PD‑FS images; a retraction greater than 5 mm often predicts a more complex reconstruction.

5. Document concomitant lesions – Explicitly note any subacromial‑bursal fluid, glenohumeral effusion, or cartilage abnormalities, as these findings may influence the choice of arthroscopic versus open techniques Most people skip this — try not to..

6. Provide quantitative dimensions – When feasible, state the width of the tendon remnant, the thickness of the fatty band, and the extent of subacromial fluid collection in millimeters; such numbers enable objective monitoring over time.

7. Encourage longitudinal comparison – Request prior imaging when available and comment on any progression of fatty infiltration or tear size, because incremental change can be a decisive factor in deciding on operative versus reparative strategies Small thing, real impact. No workaround needed..

Conclusion

Accurate depiction of rotator‑cuff pathology extends beyond simply labeling a tear as “present” or “absent.” By integrating a semi‑quantitative fatty infiltration stage, meticulously describing the morphology and signal behavior of the defect, and correlating imaging findings with the patient’s clinical picture, the radiologist furnishes surgeons with the granular data needed for individualized treatment planning. Including associated intra‑articular and peri‑tendinous pathology, employing consistent anatomic references, and offering reproducible measurements all contribute to a standardized report that enhances decision‑making, facilitates objective outcome assessment, and ultimately improves patient care.