Shoulder Injection and Aspiration OSCE — Subacromial and Glenohumeral Technique

Why This Station Is Tested

Joint injection and aspiration are core procedural skills tested in musculoskeletal and rheumatology OSCE stations. The shoulder is one of the most commonly injected joints in clinical practice. This station tests anatomy knowledge, procedural technique, consent, sterile procedure, and post-procedure management.

Indications

Subacromial injection (most common):

• Rotator cuff tendinopathy / subacromial impingement syndrome
• Subacromial bursitis
• Partial thickness rotator cuff tears

Glenohumeral joint injection:

• Glenohumeral osteoarthritis
• Adhesive capsulitis (frozen shoulder) — distension ± steroid
• Inflammatory arthritis (RA, seronegative)

Before the Procedure

Consent

Explain: the procedure, the drug being injected (steroid + local anaesthetic), benefits, and risks.

Risks to discuss:

• Post-injection flare (worsening pain for 24–48 hours after injection — common)
• Infection (rare ~1:50,000 with sterile technique)
• Tendon weakening or rupture (risk is higher with multiple injections or direct tendon injection)
• Skin depigmentation / subcutaneous fat atrophy at injection site
• Transient rise in blood glucose (warn diabetics)
• Systemic steroid effects (minimal with single injection)

Contraindications

• Suspected infection (septic arthritis)
• Overlying skin infection or psoriatic plaque
• Anticoagulation (relative — discuss risk-benefit)
• Allergy to local anaesthetic or steroid
• More than 3 injections in the same joint within 12 months (tendon weakening risk)

Drugs

Common regimen: methylprednisolone 40 mg (1 ml) + lidocaine 1% (5 ml) — mix in the same syringe.

Subacromial Injection — Technique

Landmark: posterior approach (most common for OSCE).

1. 1Patient seated, arm relaxed at side (or slight internal rotation)
2. 2Identify the posterior angle of the acromion (the flat bone at the top of the shoulder)
3. 3Mark a point 2 cm inferior and 2 cm medial to the posterior acromial angle (or just below and medial to the posterior acromial tip)
4. 4Clean with chlorhexidine in a circular motion, allow to dry
5. 5Warn the patient: "Sharp scratch now"
6. 6Insert 21G needle horizontally, aiming toward the coracoid process anteriorly, parallel to the undersurface of the acromion
7. 7If resistance is met, withdraw slightly — you may be in rotator cuff (do not inject under resistance)
8. 8If free flow — inject slowly; check for patient comfort
9. 9Withdraw, apply gentle pressure, cover with dressing

Post-Procedure Instructions

• Relative rest for 24–48 hours (avoid strenuous shoulder use)
• Post-injection flare may occur — manage with simple analgesia
• Full benefit in 1–2 weeks
• Monitor blood glucose if diabetic
• Return if: increasing redness, swelling, fever (suggests infection)
• Maximum frequency: 3 injections per joint per year

Frequently Asked Questions

"What are the landmarks for a subacromial injection via the posterior approach?"

The posterior approach to the subacromial space uses the posterior angle of the acromion as the key landmark. With the patient seated and their arm relaxed at the side, identify the bony posterior corner of the acromion. The injection point is 2 cm inferior (caudal) and 2 cm medial to this landmark. The needle (21G, 38 mm) is inserted horizontally, aiming anteriorly toward the coracoid process, and advanced parallel to the undersurface of the acromion into the subacromial bursa. If no resistance is felt, the needle tip is in the bursa and injection should proceed smoothly. Resistance suggests the needle tip is in the rotator cuff — withdraw 1–2 mm before injecting.

"What is a post-injection flare and how do you counsel the patient about it?"

A post-injection flare is a transient worsening of pain and inflammation lasting 24–72 hours after a corticosteroid injection, occurring in approximately 2–10% of cases. It is thought to be caused by a crystal-induced inflammatory reaction to the steroid preparation. Counsel the patient before the procedure: "Your shoulder may feel worse for the first day or two after the injection — this is a normal reaction and should settle. Use ice packs, rest the shoulder, and take simple painkillers like paracetamol or ibuprofen. The full benefit of the steroid injection usually takes 1–2 weeks to develop." Reassure the patient that a flare does not mean the injection has failed or caused harm.

"When is a shoulder injection absolutely contraindicated?"

Absolute contraindications to shoulder injection are: suspected septic arthritis (infection within the joint space — steroid injection would suppress the immune response and accelerate joint destruction); overlying skin infection, cellulitis, or broken skin at the injection site; known allergy to the drugs being injected (steroid or local anaesthetic). Relative contraindications include: anticoagulation (risk of haemarthrosis — discuss individually), poorly controlled diabetes mellitus (steroid causes transient blood glucose rise), previous reaction to joint injection, prosthetic joint (risk of periprosthetic infection is significant), and pregnancy. In an OSCE, always ask about allergies, infections, anticoagulation, and diabetes before proceeding.

"How many corticosteroid injections can be given to the same joint and why is there a limit?"

The generally accepted limit is three injections per joint per year (or no more than 3–4 in the patient's lifetime in the same joint, per some guidelines). This limit exists because repeated corticosteroid injections cause progressive weakening of tendons, cartilage degeneration, and potentially accelerated joint damage. Direct injection into a tendon (rather than the bursa) carries a particular risk of tendon rupture. Subcutaneous fat atrophy and skin depigmentation can also occur at the injection site, particularly in darker-skinned individuals. If a patient requires more than three injections in 12 months, reconsider the diagnosis and consider referral for physiotherapy, imaging, or surgical review.

"What would make you suspect septic arthritis and how would you manage it?"

Septic arthritis should be suspected when a joint is hot, swollen, extremely tender, and the patient is systemically unwell with fever, rigors, and elevated inflammatory markers (CRP, WCC). Risk factors include: IV drug use, immunosuppression, recent joint injection or surgery, adjacent soft tissue infection, rheumatoid arthritis (increased susceptibility), and bacteraemia from any source (UTI, endocarditis). Never inject steroid into a joint where septic arthritis is suspected — it will worsen the infection. Instead, aspirate the joint under sterile conditions and send fluid for urgent Gram stain and culture, glucose, protein, and crystal analysis. Start IV antibiotics after cultures are taken (do not wait for results if the patient is acutely unwell). Orthopaedic referral for surgical washout is often required.

"What is the difference between subacromial impingement and adhesive capsulitis on history?"

Subacromial impingement presents with a painful arc of abduction (60–120°), pain worse with overhead activities and lying on the affected shoulder, and tenderness below the anterolateral acromion. Passive range of movement is relatively preserved — the pain occurs in the arc rather than with all movements. Adhesive capsulitis (frozen shoulder) presents with a gradual progressive loss of both active AND passive range of movement in all planes, particularly external rotation. The condition passes through three phases: freezing (painful, progressive restriction over 2–9 months), frozen (stiffness plateau, pain begins to ease, lasting 4–12 months), and thawing (gradual recovery over 12–42 months). Injection for impingement targets the subacromial space; injection for adhesive capsulitis may be into the glenohumeral joint with a larger volume (distension arthrogram) to stretch the contracted capsule.

Related guides: Shoulder Examination OSCE · GALS Screening Examination OSCE · Musculoskeletal History OSCE · Consent and Capacity OSCE · Septic Arthritis OSCE