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Home / Station 30: Painful swollen knee

NAC OSCE preparation

Station 30: Painful swollen knee

Complete the task in 11 minutes. Reveal the full standardized-patient script, examiner prompts and structured debrief only after your attempt.

Station time

11:00

Ready for an 11-minute attempt.

Candidate instructions

Painful swollen knee

11 minutes

Discipline: Physical Examination
Station type: Focused musculoskeletal exam
Setting: Emergency department

Your task

Perform a focused examination of the painful right knee, then state your differential and immediate management.

Information available at entry

HR 112/minBP 118/70 mm HgRR 20/minT 38.5°CSpO₂ 98% room air

Coach prompt: Recognize septic arthritis and arrange urgent aspiration and treatment.

In Exam Mode, coaching cues are hidden. Ask a partner to use the standardized-patient script after you start the timer.

Finished your attempt?Reveal the full station only after completing or stopping the timer.

Complete station package

Standardized-patient script and structured debrief

Station 30 of 30

Standardized-patient profile

NameMr. Peter Singh

Age57

Pronounshe/him

RolePatient

Demeanour: In severe pain and reluctant to move the knee.

Opening statement: “My knee became very painful and swollen overnight. I can barely move it.”

History and standardized-patient responses

Information if requested after exam

Candidate explores	Standardized-patient response
Onset	Acute over 12 hours; no major trauma.
Risk	Diabetes and recent skin infection on shin.
History	Prior gout in first toe, never in knee.
Systemic	Rigors and malaise.

Physical findings

Right knee held slightly flexed.
Large warm effusion with erythema.
Severe pain with even small passive range of motion.
Unable to weight-bear.
No open wound over aspiration site.
Small healing abrasion on ipsilateral shin.
Hip movement does not reproduce pain; distal neurovascular status intact.

Examiner prompts

Most concerning diagnosis?

Septic arthritis until proven otherwise.

Key test?

Urgent sterile arthrocentesis for cell count/differential, Gram stain/culture and crystals; obtain blood cultures.

Antibiotics?

After cultures/aspiration when this will not cause unsafe delay; start promptly if septic/systemically ill and involve orthopedics for drainage.

Differential diagnosis

Septic arthritis
Crystal arthritis
Hemarthrosis
Inflammatory arthritis
Occult fracture or internal derangement
Cellulitis/bursitis

Investigations

Synovial WBC/differential, Gram stain and culture
Crystal analysis—crystals do not exclude infection
Blood cultures before antibiotics when feasible
CBC, CRP/ESR, renal function and lactate if ill
Plain radiograph and ultrasound only as adjuncts

Management

Analgesia and sepsis care
Urgent arthrocentesis
Empiric IV antibiotics after cultures/aspiration if safe
Orthopedic consultation for washout/drainage
Adjust therapy to cultures
Manage glucose and infection source

Communication behaviours

Warn before touching or moving painful joint
Acknowledge pain and stop unnecessary maneuvers
Explain urgency of aspiration

Critical safety actions

Do not discharge presumed gout without excluding infection
Do not delay antibiotics in a septic patient
Crystals can coexist with infection

Model closing summary

The hot, acutely swollen knee, fever, inability to bear weight and marked pain with passive movement make septic arthritis the leading diagnosis. I would provide analgesia, assess and treat sepsis, obtain blood cultures and urgent sterile synovial fluid for cell count, Gram stain, culture and crystals, then start prompt empiric IV antibiotics and involve orthopedics for definitive drainage.

Common pitfalls

Forceful range of motion
Relying on serum urate
Delaying aspiration for MRI
Injecting steroid before infection is excluded

Reference starting points

Verify current recommendations and local protocols before clinical use.

Continue practising

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