The Daily Differential — Thursday, May 7, 2026

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Elbow Arthrocentesis and Intra-Articular Injections

A hot swollen elbow may be septic arthritis until proven otherwise; arthrocentesis is both diagnostic and sometimes therapeutic. Missing septic arthritis...

At the Bedside

Indications for elbow arthrocentesis:
Suspected septic arthritis.
Crystal arthritis diagnosis.
Unexplained atraumatic effusion.
Hemarthrosis evaluation.
Therapeutic decompression in select cases.
Contraindications/relative contraindications:
Overlying cellulitis at puncture site — choose alternate approach if possible.
Uncorrected severe coagulopathy is relative; anticoagulation alone is not always absolute.
Prosthetic joint: discuss with orthopedics before aspiration if possible.
Key exam findings:
Pain with passive ROM, especially flexion/extension.
Effusion, warmth, erythema.
Limited ROM; septic arthritis usually hurts throughout arc.
Compare bursitis: olecranon bursitis is posterior swelling with often more preserved joint ROM.
Workup:
X-ray before aspiration if trauma, suspected fracture, prosthesis, or unclear anatomy.
Labs: CBC, ESR/CRP, blood cultures if febrile/systemically ill.
Synovial fluid: cell count with differential, Gram stain, culture, crystals. Consider glucose/protein less helpful acutely.
POCUS can identify effusion and guide needle placement.
Procedure technique: lateral “soft spot”:
Position elbow flexed ~90 degrees, forearm pronated or neutral.
Identify triangle: lateral epicondyle, radial head, olecranon.
Sterile prep, local anesthesia.
Insert needle into soft spot, aiming toward joint space.
Aspirate fluid; do not inject steroid until infection is confidently excluded.
Intra-articular injections:
Steroid injections are generally for inflammatory/degenerative conditions, not undifferentiated hot joint.
Avoid if suspected infection, fracture, bacteremia, overlying cellulitis, or prosthetic joint without specialist input.
Disposition:
Septic arthritis suspected: IV antibiotics after cultures/aspiration when feasible, ortho consult, admit.
Crystal arthritis with reassuring exam: NSAID/colchicine/steroid plan and outpatient follow-up.
Traumatic hemarthrosis: evaluate for occult fracture/ligament injury; immobilize and refer as needed.

A Classic Presentation

A 67-year-old man with diabetes presents with fever and a painful swollen elbow. He has severe pain with passive ROM and a small effusion on POCUS. X-ray shows no fracture. Arthrocentesis from the lateral soft spot yields cloudy fluid with high WBC count and neutrophil predominance. Blood cultures are obtained, vancomycin plus ceftriaxone is started, orthopedics is consulted, and the patient is admitted for septic arthritis management.

Study Directive

On a skeleton or diagram, mark the lateral epicondyle, radial head, olecranon, and “soft spot.”
Memorize the synovial fluid studies: cell count/diff, Gram stain, culture, crystals.
Watch one procedural video of elbow arthrocentesis and write your sterile setup checklist.
Review your institution’s empiric septic arthritis antibiotic pathway and renal dosing notes.

Key Medications

Local anesthesia:
- Lidocaine 1%: infiltrate 3–10 mL; max 4.5 mg/kg without epi, 7 mg/kg with epi. Avoid intra-articular epi when possible.
- Bupivacaine 0.25–0.5%: 3–10 mL; max ~2.5 mg/kg without epi. Check reference if using larger volumes.
Empiric septic arthritis antibiotics, adult examples:
- Vancomycin: 15–20 mg/kg IV, typically q8–12h after loading depending renal function; check institutional dosing.
- Add gram-negative coverage if risk factors:
- Ceftriaxone: 2 g IV q24h, or
- Cefepime: 2 g IV q8–12h for broader coverage; adjust renal dosing.
Intra-articular steroid examples if infection excluded:
- Triamcinolone acetonide: commonly 10–40 mg intra-articular for medium joints; dosing varies — verify with institutional protocol/reference.
- Methylprednisolone acetate: commonly 20–40 mg intra-articular; verify dosing.

High-Yield Pearls

Septic arthritis and crystal arthritis can coexist; crystals do not exclude infection.
Olecranon bursitis causes posterior swelling and may preserve joint ROM better than true septic arthritis.
Do not inject intra-articular steroids into an undifferentiated hot joint.

Board Question

Which synovial fluid test is most important to obtain when septic arthritis is suspected?

AProtein concentration
BCulture
CRheumatoid factor
DSerum uric acid

Reveal answer

Correct: B

Synovial fluid culture is essential for identifying the organism and tailoring therapy. Cell count, Gram stain, and crystals are also important, but serum uric acid does not rule in or rule out acute gout.

Recent Literature

Review or guideline Acute Monoarthritis: Diagnosis in Adults
Am Fam Physician, 2025 · cited 1×

Reinforces the ED approach to an acutely swollen elbow: suspect septic arthritis or crystal disease, obtain synovial fluid for cell count, Gram stain/culture, and crystals when infection is possible, and avoid relying on serum tests alone.

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Elbow Dislocations

Elbow dislocation is the second most common major joint dislocation in adults and can threaten the brachial artery and median/ulnar nerves. Early reduction...

At the Bedside

Mechanism: Usually fall on outstretched hand. Most are posterior/posterolateral.
Classification:
Simple: no associated fracture.
Complex: associated fractures, commonly radial head, coronoid, olecranon, distal humerus.
“Terrible triad”: elbow dislocation + radial head fracture + coronoid fracture.
Exam before reduction:
Inspect deformity, skin tenting/open injury.
Neurovascular exam:
Median nerve/AIN: thumb IP flexion, index DIP flexion, “OK sign.”
Ulnar nerve: finger abduction/adduction.
Radial/PIN: wrist/finger extension.
Pulses, cap refill, hand warmth.
Document before and after reduction.
Imaging:
AP/lateral elbow X-rays before reduction unless vascular compromise demands immediate reduction.
Look for associated fractures, joint alignment.
Post-reduction X-rays mandatory.
CT if complex fracture pattern or surgical planning needed.
Reduction:
Provide adequate analgesia/sedation.
Common posterior reduction: traction-countertraction with elbow flexion, gentle correction of medial/lateral displacement, pressure on olecranon anteriorly.
Avoid repeated forceful attempts.
After reduction:
Repeat neurovascular exam.
Assess stability through gentle ROM.
Immobilize in posterior long arm splint at ~90 degrees flexion, forearm neutral/pronation depending stability.
Early ortho follow-up; simple stable dislocations need brief immobilization then early ROM to prevent stiffness.
Disposition:
Discharge if simple, stable, closed, neurovascularly intact after reduction, pain controlled, reliable follow-up.
Admit/urgent ortho for open dislocation, irreducible dislocation, vascular compromise, nerve deficit, compartment syndrome concern, unstable joint, or associated fracture requiring surgery.

A Classic Presentation

A 24-year-old man falls from a skateboard onto an outstretched hand and presents with obvious elbow deformity. He has intact pulses and normal median, ulnar, and radial nerve function. X-ray shows posterior elbow dislocation without fracture. Under procedural sedation, the elbow is reduced with traction-countertraction. Post-reduction films confirm alignment, neurovascular exam remains normal, and he is placed in a posterior long arm splint with orthopedic follow-up.

Study Directive

Practice a complete distal neurovascular exam: median/AIN, ulnar, radial/PIN, pulses, cap refill.
Review posterior elbow dislocation reduction steps and complications.
Look at 10 elbow X-rays and identify normal radiocapitellar and ulnohumeral alignment.
Memorize urgent ortho indications: open, vascular, nerve deficit, irreducible, unstable, complex fracture.

Key Medications

Analgesia:
- Fentanyl: 0.5–1 mcg/kg IV q5–10 min PRN; monitor respirations.
- Morphine: 0.05–0.1 mg/kg IV q10–20 min PRN.
- Hydromorphone: 0.2–0.5 mg IV q15–30 min PRN; titrate cautiously.
Procedural sedation options:
- Propofol: 0.5–1 mg/kg IV initial, then 0.25–0.5 mg/kg boluses; requires full sedation monitoring.
- Ketamine: 1–2 mg/kg IV or 4–5 mg/kg IM.
- Etomidate: 0.1–0.15 mg/kg IV; some use 0.2 mg/kg — practice varies.
Post-reduction pain:
- Ibuprofen: 400–600 mg PO q6h PRN.
- Acetaminophen: 650–1000 mg PO q6h PRN.

High-Yield Pearls

The elbow gets stiff quickly; stable simple dislocations need early ROM after short immobilization.
Brachial artery injury can occur even with palpable collateral flow — reassess perfusion carefully.
The “terrible triad” is unstable and usually needs orthopedic operative management.

Board Question

After reducing a posterior elbow dislocation, what is the most important next step?

AImmediate discharge without imaging if pain improves
BPost-reduction neurovascular exam and radiographs
CSling only and unrestricted ROM
DIntra-articular steroid injection

Reveal answer

Correct: B

Reduction can reveal or cause neurovascular injury, and post-reduction radiographs confirm alignment and identify associated fractures. Documentation before and after reduction is essential.

Recent Literature

Review or guideline Managing Elbow Dislocations
Ann Emerg Med, 2022 · cited 5×

EM-focused review covering neurovascular assessment, radiographs for associated fractures, procedural sedation/reduction, post-reduction stability testing, splinting, and early follow-up for simple versus complex elbow dislocations.

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Elbow Fractures

Elbow fractures range from subtle radial head fractures to limb-threatening supracondylar injuries. The ED must identify occult fractures, protect...

At the Bedside

Mechanisms: FOOSH, direct blow, fall onto flexed elbow, high-energy trauma.
Exam essentials:
Inspect swelling, deformity, wounds.
Palpate distal humerus, olecranon, radial head, epicondyles.
Assess active/passive ROM; inability to fully extend suggests fracture.
Neurovascular exam:
Median/AIN, ulnar, radial/PIN.
Radial/ulnar pulses, cap refill, hand temperature.
Watch for compartment syndrome in high-energy injuries.
Imaging:
AP/lateral elbow X-rays; add oblique/radial head-capitellum views if needed.
Fat pad signs:
Posterior fat pad = fracture until proven otherwise.
Anterior “sail sign” suggests effusion.
Radiocapitellar line should intersect capitellum on all views.
Anterior humeral line in children should intersect middle third of capitellum.
CT for complex intra-articular fractures or operative planning.
Common adult elbow fractures:
Radial head/neck: lateral elbow pain, pain with pronation/supination. Nondisplaced: sling or posterior splint briefly, early ROM, ortho follow-up. Mechanical block/comminution/displacement: ortho.
Olecranon: posterior pain/swelling; inability to actively extend elbow suggests extensor mechanism disruption. Displaced fractures often operative.
Coronoid: often associated with dislocation/instability; ortho.
Distal humerus: often high energy in adults/fragility in elderly; frequently operative.
High-yield pediatric injuries:
Supracondylar fracture: fall on outstretched hand; assess brachial artery and AIN. Type II/III or neurovascular compromise = urgent ortho.
Lateral condyle fracture: can be subtle; often requires ortho due to nonunion risk.
Medial epicondyle fracture: associated with elbow dislocation; fragment can be incarcerated in joint.
Initial management:
Analgesia, ice, elevation.
Immobilize:
Most elbow fractures: posterior long arm splint at ~90 degrees flexion.
Avoid excessive flexion if swelling or vascular compromise.
Open fracture: sterile dressing, IV antibiotics, tetanus, urgent ortho.
Disposition:
Discharge: closed, nondisplaced, neurovascularly intact, pain controlled, reliable ortho follow-up.
Urgent ortho/admit: open fracture, neurovascular deficit, compartment syndrome, displaced/intra-articular fracture, mechanical block, elbow instability/dislocation, pediatric displaced supracondylar fracture.

A Classic Presentation

A 58-year-old woman falls on an outstretched hand and presents with lateral elbow pain. She can flex and extend partially but has marked pain with pronation/supination. X-ray shows a posterior fat pad and subtle nondisplaced radial head fracture. She is neurovascularly intact. She receives analgesia, a sling or brief posterior splint depending pain, instructions for early ROM, and outpatient orthopedic follow-up.

Study Directive

Review normal elbow X-ray lines: radiocapitellar line, anterior humeral line, fat pads.
Identify the ED management of radial head, olecranon, distal humerus, and supracondylar fractures.
Practice posterior long arm splint positioning and document neurovascular status pre/post splint.
Create a “must-call ortho” checklist for elbow trauma.

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Mechanism Pearl of the Day: The elbow and wrist are small anatomic spaces where pressure and alignment matter: median nerve compression in the carpal tunnel, capsular distension in elbow effusion, neurovascular stretch during dislocation, and occult intra-articular fractures all produce symptoms by disrupting tight relationships between bone, ligament, tendon, nerve, and vessel.

Key Medications

Pain control:
- Acetaminophen: 650–1000 mg PO q6h PRN; max 3000–4000 mg/day depending patient risk.
- Ibuprofen: 400–600 mg PO q6h PRN.
- Ketorolac: 15 mg IV/IM commonly used; some settings use 30 mg IV/IM in selected adults, but lower dosing is often preferred due adverse effects.
- Oxycodone: 5 mg PO q4–6h PRN severe pain; use short course if needed.
Open fracture antibiotics:
- Cefazolin: 2 g IV q8h; 3 g IV if ≥120 kg.
- Add gram-negative coverage for severe contamination/type III injuries per protocol, e.g. gentamicin 5 mg/kg IV once daily with renal monitoring — verify institutional protocol.
- Farm/soil contamination: add anaerobic coverage, e.g. piperacillin-tazobactam 4.5 g IV or protocol-specific regimen.
Tetanus:
- Tdap/Td: 0.5 mL IM if indicated.
- TIG: 250 units IM for dirty wounds if immunization incomplete/unknown.

High-Yield Pearls

Adult traumatic posterior fat pad = occult fracture until proven otherwise.
Radial head fractures hurt most with pronation/supination because the radial head rotates against the capitellum.
In pediatric supracondylar fractures, always document AIN function and perfusion before and after splinting.

Board Question

An adult has elbow pain after a FOOSH. X-ray shows no obvious fracture but demonstrates a posterior fat pad sign. What is the best interpretation?

ANormal finding in adults
BOccult intra-articular fracture
CIsolated ligament sprain only
DSeptic arthritis

Reveal answer

Correct: B

A posterior fat pad after trauma indicates elbow effusion and should be treated as an occult fracture, commonly radial head fracture in adults. Immobilize appropriately and arrange follow-up.

Recent Literature

Review or guideline Radiographic Evaluation of Elbow Fractures
Semin Musculoskelet Radiol, 2021 · cited 1×

Useful for ED fracture detection: reinforces systematic elbow radiograph reading, including alignment lines, fat-pad signs, and when an occult fracture should be immobilized despite subtle films.

TheDaily Differential

Carpal Tunnel Syndrome

At the Bedside

Study Directive

Recent Literature

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Elbow Arthrocentesis and Intra-Articular Injections

Elbow Dislocations

Elbow Fractures

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