Radiology glossary

Rotator Cuff Tear — What It Means on Your Report

Part of: Shoulder findings, explained

One of the tendons that steadies your shoulder is torn, which can cause pain and weakness when lifting your arm.

In plain English: a tear in the shoulder’s rotator cuff tendons.

What it means on MRI

MRI is the most complete test for rotator cuff tears: it shows each tendon, distinguishes partial-thickness from full-thickness tears, measures retraction in centimeters, and — uniquely — shows the muscle behind the tear, including atrophy and fatty infiltration that determine whether a tear is even repairable. It also reveals the usual companions: bursitis, labral tears, arthritis, and cysts. When the full surgical picture is needed, MRI is the test.

What it means on CT

CT is not a cuff test — tendons are poorly seen. Its shoulder role is bony: fractures, arthritis, and surgical planning. A CT arthrogram (dye injected into the joint) can outline a full-thickness tear as dye leaking where it should not, and is occasionally used when MRI is impossible, but it is invasive and rarely first-line.

What it means on X-ray

X-ray cannot show the cuff tendons, but every shoulder workup starts here for good reason: it shows arthritis, calcific deposits, the shape of the acromion, and — importantly — the space between the humeral head and acromion. A narrowed acromiohumeral interval hints at a large chronic tear with the ball riding upward. X-ray sets the bony stage; MRI or ultrasound examines the tendons.

What it means on Ultrasound

Ultrasound is genuinely excellent for rotator cuff tears in experienced hands: it is dynamic (the tendon can be watched moving), it compares sides in seconds, it finds bursitis and calcifications, and it guides injections precisely. For full-thickness tears its accuracy rivals MRI. Its weakness is the deep structures and the muscle behind the tear — fatty infiltration and atrophy, which matter enormously for planning, are MRI territory.

What radiologists look at next

The radiologist identifies which tendon (supraspinatus most often, then infraspinatus, subscapularis, teres minor), measures the tear's width and retraction in two planes, and classifies partial tears by surface — bursal-sided, articular-sided, or intrasubstance — and by percentage of thickness. For full-thickness tears they grade the muscle: atrophy and fatty infiltration (Goutallier 0-4), because a grade 3-4 muscle changes everything. They check the tear's companions — subacromial bursitis, biceps tendon problems, labral tears, cysts (a ganglion near the spinoglenoid notch hints at a labral tear), and arthritis — and note the acromion's shape, which frames the impingement story.

Where it commonly shows up

• right shoulder
• left shoulder
• shoulder
• supraspinatus

Questions to ask your doctor

• What treatment options exist for rotator cuff tear at the affected area?
• Is my tear partial or full-thickness — and which tendon is involved?
• How far has the tendon retracted, and what is the muscle's condition?
• Could my pain be from bursitis or tendinosis rather than the tear itself?
• Should I see a shoulder specialist, and how soon?
• What movements should I avoid until I have a plan?

Common questions

Can a rotator cuff tear heal on its own?

Torn tendon ends do not reattach by themselves — but many tears, especially degenerative partial ones, become painless and stay stable without intervention. 'Healing' and 'doing well' are different things: plenty of people do well with a tear that is still there on MRI. Your doctor judges by function, not by the image.

Why does it hurt more at night?

Night pain is classic for cuff problems: lying on the shoulder compresses the inflamed structures, and the lack of daytime distraction makes pain more noticeable. It is a common and recognized pattern — mention it to your doctor, as it helps complete the picture.

What does 'full-thickness' mean? Is the tendon in two pieces?

Full-thickness means the tear goes all the way through the tendon from one surface to the other — but the tendon may still be in continuity at the edges, or it may be retracted. The report's measurements of retraction and the muscle's condition matter more than the label itself.

My report says tendinosis, not a tear. What is the difference?

Tendinosis is wear and thickening of the tendon without a discrete tear — the fibers are disorganized but continuous. It is the stage before tearing and is very common with age. Many painful shoulders have tendinosis plus bursitis and no tear at all.

What each test can miss

Where MRI can mislead

MRI's signature pitfall is magic angle artifact: when the supraspinatus tendon courses at about 55 degrees to the magnetic field, it lights up falsely and can mimic a partial tear — radiologists double-check on sequences less prone to it before calling a tear. Tendinosis (worn, bright tendon) versus small partial tear is another genuinely hard borderline; reports hedge with 'fraying versus low-grade partial tear' and mean it. Muscle fatty infiltration (the Goutallier grade) is the finding patients overlook and surgeons care about most — a retracted tear with a fatty, atrophied muscle may not be repairable no matter what the tendon looks like.

Where CT can mislead

CT's pitfall is irrelevance to the cuff: without arthrography it cannot show tendons, so a 'normal' shoulder CT never excludes a tear. CT arthrography can show full-thickness tears via dye leakage but misses partial tears and says nothing about muscle quality.

Where X-ray can mislead

X-ray's pitfall is the normal film: most cuff tears have a completely normal X-ray, because tendons are invisible. The indirect signs — superior migration of the humeral head, acromial spurring — appear only in large chronic tears, so their absence means nothing. Do not let a normal X-ray reassure you about the tendons.

Where Ultrasound can mislead

Ultrasound's pitfall is operator dependence: in expert hands it rivals MRI for full-thickness tears; in inexperienced hands it misses them. Anisotropy — the probe angle making a healthy tendon look dark and torn — is the classic false positive, fixed by rocking the probe. And ultrasound cannot reliably grade the muscle's fatty infiltration behind a big tear, which is why large tears usually still get an MRI.

How radiologists tend to phrase it

The lines below are fictional illustrations of common report phrasing — not real patient reports.

Full-thickness tear of the supraspinatus with 2.5 cm retraction and Goutallier grade 2 fatty infiltration.

The top tendon is completely torn and has pulled back 2.5 cm, with moderate fatty replacement of its muscle. The retraction and the muscle grade — not just 'full-thickness' — are what determine options.

Bursal-sided partial-thickness tear involving approximately 50% of tendon thickness.

A tear on the upper surface of the tendon going about halfway through. 'Bursal-sided' versus 'articular-sided' (underside) matters because the two behave differently.

Tendinosis with fraying versus low-grade articular-sided partial tear.

The tendon is worn and frayed; the radiologist cannot confidently distinguish advanced wear from a small underside tear. This honest hedge is common and appropriate — the borderline is genuinely blurry.

Intact rotator cuff with subacromial-subdeltoid bursitis.

The tendons are whole, but the bursa above them is inflamed. This is good news wrapped in a diagnosis: bursitis explains pain without any tear at all.

What your doctor might do next

Your doctor will examine the shoulder themselves — testing strength in specific rotations, checking range of motion, and looking for the lag signs that reveal a tendon not doing its job — because the exam plus your story determines what the MRI finding means. Many degenerative partial tears, especially in older shoulders, are managed without procedures; traumatic tears and tears with weakness in younger shoulders get a prompter specialist look. If the report mentions significant retraction or fatty infiltration of the muscle, bring that up explicitly — those details shape the specialist conversation more than the word 'tear' alone. Describe what your shoulder cannot do (reach overhead? sleep on that side? lift?) and ask your doctor to connect the tear's size and location to your specific deficits.

This is general information only — talk to your doctor about what it means for you.

Related conditions

• Labral Tear — What It Means on Your Report
• Fracture — What It Means on Your Report
• Joint Effusion — What It Means on Your Report