For an average 70‑kg adult receiving an intra‑articular or subacromial shoulder injection, how many milliliters of 1 % lidocaine and how many milligrams of Kenalog (triamcinolone acetonide) should be used?

Shoulder Injection Dosing: Lidocaine and Triamcinolone

For an intra-articular or subacromial shoulder injection in a 70-kg adult, use 4–6 mL of 1% lidocaine (40–60 mg) combined with 40 mg of triamcinolone acetonide (Kenalog). 1, 2

Standard Dosing Protocol

Corticosteroid Component

• Triamcinolone acetonide 40 mg is the evidence-based dose for shoulder injections, whether targeting the subacromial bursa or glenohumeral joint 1, 3
• This dose (40 mg) provides significantly superior pain relief and functional improvement compared to lower doses (10 mg) in controlled trials 3
• Do not reduce the corticosteroid dose in diabetic patients; instead, counsel them about transient hyperglycemia and instruct glucose monitoring for 1–3 days post-injection 4

Local Anesthetic Component

• Use 4–6 mL of 1% lidocaine (40–60 mg total) mixed with the corticosteroid 1, 2
• The 4 mL volume is non-inferior to 10 mL for pain outcomes and functional scores, making it the preferred lower-volume option 2
• For a 70-kg adult, the maximum safe lidocaine dose without epinephrine is 315 mg (4.5 mg/kg), and with epinephrine is 490 mg (7.0 mg/kg), so 40–60 mg is well within safety limits 5, 6
• Warming lidocaine to 37°C before injection reduces infiltration pain 5, 4

Practical Injection Technique

Preparation and Safety

• Calculate maximum allowable lidocaine dose before administration: for this 70-kg patient, 315 mg without epinephrine or 490 mg with epinephrine 7, 6
• Use strict aseptic technique: surgical gloves, skin preparation with alcohol/iodine/chlorhexidine, and change needles between drawing medication and injecting 5, 4
• Avoid lidocaine administration within 4 hours of other local anesthetic interventions to prevent cumulative toxicity 5

Mixture Preparation

• Combine 40 mg triamcinolone acetonide (typically 1 mL of 40 mg/mL suspension) with 4 mL of 1% lidocaine for a total volume of 5 mL 1, 2
• Alternatively, use 6 mL total volume (2 mL triamcinolone 40 mg/mL + 4 mL lidocaine 1%) if preferred 1

Clinical Context and Caveats

Injection Accuracy

• Only 70% of "subacromial" injections actually reach the subacromial bursa using landmark-based techniques 8
• However, pain relief occurs whether the injection reaches the subacromial bursa or deltoid muscle, suggesting local tissue effects contribute to efficacy 8
• Consider ultrasound or fluoroscopic guidance to improve targeting accuracy 6

Special Populations

• Diabetic patients: Use the full 40 mg dose but warn about transient blood glucose elevation (typically days 1–3 post-injection); no severe events like ketoacidosis have been reported 4
• Patients with prosthetic joints: Avoid routine injections due to higher infection risk 5
• Pre-surgical patients: Perform injections at least 3 months before planned joint replacement to minimize infection risk 5, 6

Post-Injection Instructions

• Advise patients to avoid overuse for 24 hours but discourage complete immobilization 5, 4
• Limit injection frequency to 3–4 injections per year in the same joint 5
• The risk of septic arthritis after intra-articular injection is very low (0.035%) 6

Common Practice Variations

• Surgeons tend to use larger anesthetic volumes (up to 10 mL) compared to rheumatologists and physiatrists, possibly to better assess the percentage of pain attributable to the injected region 9
• However, the 4 mL volume provides equivalent pain relief with less medication exposure 2