Shoulder Ultrasound
Reference: Musculoskeletal Ultrasound: Anatomy and Technique, Springer 2008.
Setup
- High-frequency linear probe. Use a lower-frequency curved probe for large patients.
- Patient sits on a stool, facing the ultrasound machine.
- Stand behind the patient so the probe stays below your own shoulder level.
- Shoulder fully exposed.
- Scan every tendon in two planes: long axis and short axis.
- Compare with the other side whenever you are unsure.
Scan sequence
1. Long head of biceps tendon (LHBT)
Position: elbow flexed 90 degrees, forearm supinated, hand resting on the thigh or pillow. This turns the bicipital groove forward. Sometimes you might need to slightly externally rotate the shoulder to expose more of the bicipital groove.
Short axis first: a round bright tendon sitting between the lesser and greater tuberosities (‘A valley between 2 hills’). Then long axis down to the musculotendinous junction.
Heel-toe: gently press the lower end of the probe. A normal tendon turns from patchy dark to evenly bright and fibrillar.
Dynamic: elbow at your side, rotate the arm in and out in short axis. The tendon must stay in the groove. Subluxation may only show with movement.
Follow the sheath to its lowest point. Fluid may collect there.
If there is fluid, correlate clinically (tenderness & special test) as fluid does not always mean Biceps tendinopathy. The fluid may track down from a torn Supraspinatus tendon.
2. Subscapularis
Arm externally rotated, elbow at the side.
Long axis: tendon runs from under the coracoid to the lesser tuberosity. Sweep up and down. Short axis shows a multipennate (several bright slips) pattern.
Dynamic: rotate the arm in and out. This separates anisotropy from true tendinosis or a partial tear.
Move the probe medially over the coracoid and repeat to look for subcoracoid impingement or bursa fluid.
3. Supraspinatus (the tendon most often torn)
Crass position: hand behind the back, palm facing backward, elbow tucked in. This pulls the tendon out from under the acromion.
Modified Crass (Middleton): hand on the back pocket, elbow pointing backward and tucked in. This shows the anterior critical zone next to the biceps.
Find the LHBT in long axis first (rotator interval), then slide the probe backward along the supraspinatus, about 45 to 50 degrees to the coronal plane.
Normal long axis: smooth convex upper surface, not compressible, inserting onto the shelf of the greater tuberosity. Layers from deep to superficial: bone, thin dark cartilage, tendon, thin bursa and fat line, deltoid.
Turn 90 degrees for short axis and sweep front to back.
Follow the subacromial-subdeltoid bursa in every direction. Fluid often sits lateral to the greater tuberosity.
Check the muscle belly in the supraspinous fossa: thin or unusually bright compared with the other side suggests atrophy or fatty change.
Possible findings include tear (determine site, degree, any retraction if complete tear), tendinopathy, calcification, bursitis, effusion (if case of massive tear).
4. Infraspinatus, teres minor, posterior labrum
Forearm across the chest, hand on the opposite shoulder.
Infraspinatus has a long tendon. Teres minor sits below it with a short tendon (1 to 2 cm).
Posterior labrum: move the probe medially over the back of the joint. A bright triangle sits between the humeral head and glenoid. Ask the patient to tap the hand on the opposite shoulder. Fluid should never pass through the labrum.
Further medial is the spinoglenoid notch, a bony depression holding the suprascapular nerve and vessels (potential site for RFA or nerve block).
5. Acromioclavicular (AC) joint
Arm by the side, probe in the coronal plane over the joint. The clavicle sits slightly higher than the acromion. The joint is wider anteriorly.
Compare the width with the other side. Abduct and adduct the arm for a dynamic check.
6. Dynamic impingement check
Probe in the coronal plane over the lateral edge of the acromion. Start with the arm at the side, then abduct.
Normal: tendon and bursa glide under the acromion smoothly. No bunching of fibres, no bulging of the bursa, no pain or block.
Pitfalls
- Anisotropy is the commonest artifact. A dark patch that vanishes when you tilt the probe square to the fibres is normal. If it stays dark, treat it as real.
Checklist
- Patient seated on stool, shoulder exposed, you stand behind
- LHBT short and long axis, heel-toe done
- LHBT dynamic rotation: tendon stays in groove
- Subscapularis long and short axis, rotated in and out
- Supraspinatus in Crass or modified Crass positions
- Supraspinatus both planes, insertion on greater tuberosity seen
- Subacromial bursa
- Infraspinatus and teres minor, posterior labrum, spinoglenoid notch
- AC joint width compared with other side
- Dynamic impingement test done