OSCE – Procedure

1. Knee aspiration

Subject and Curriculum Reference




  • One on one tutorials


  • arthrocenthesis


Clinical Scenario Stem

A 45 year old man, John Smith, presents with a unilateral swollen painful knee. There is no history of trauma. You decide that you need to aspirate the knee to rule out septic arthritis. The patient is being seen by a competent third year resident Melissa Harvey. You are going to instruct the resident on how to do the procedure and then guide them through the procedure.

The patient and Dr. Harvey are present in the next room.

You will interact with the patient but use the model to do the actual procedure.

There will be no interaction with the examiners in the room.


Patient instructions

John Smith is a 45 year old man who has developed a painful swollen knee. He noticed some pain in his left knee yesterday and this morning when he woke it was red, swollen and very painful. He is unable to walk on it.

He has no past medical history and no history of swollen joints. Melissa Harvey is his doctor. She has taken a thorough history and examination. She has also explained what may have caused the swollen knee and that in order to diagnose the disorder they will have to take a sample of fluid from the knee. She has also explained that she has seen this done before but has not done it herself and would like to under the instruction of her consultant.

John Smith is a very easy going man. He has developed trust in Dr. Harvey and is happy for her to do the procedure under instruction.

The focus of this assessment is on the candidate teaching the junior doctor a procedure. You will have minimal interaction with the candidate apart from some specific interactions that are required:

  • We expect the candidate will explain that Dr. Harvey would like to do the procedure under instruction and ask for consent for that to occur. If this does not occur then you should say “has she ever done this before? Will you be helping her?”
  • We also expect the candidate to explain the procedure to you or ask Dr. Harvey to do that and obtain consent. If this does not happen then please say “what are you going to do?”
  • We expect the candidate to always be gentle with you. If they do something that hurts then please let them know


Junior Doctor Instructions

Melissa Harvey is a competent third year resident. She hopes to do surgery as a career. She is currently doing a 3 month rotation in Emergency Medicine and likes the experience. She is well liked, knowledgeable and good practically.

Melissa has not done a knee aspirate before but has seen a few done so has some knowledge of what to do.

You are to follow the instructions of the candidate only. However, when you follow the instructions you are competent at them. If you are unclear on an instruction then please ask to clarify.


All equipment needed is supplied.

Use model to do the procedure



  • The “Scenario” in the preceding page is ALL the information provided to the candidate before s/he interacts with the actors.
  • Candidates will only have 7 minutes to try to explain and complete the procedure. Successive candidates will be interrupted by 3-minute breaks, during which the examiners and actor discuss the preceding candidate.
  • After a succession of 10 or less candidates, there is a longer break to permit rest and refreshments


Scoring Sheet

Not met Partly met Fully met

  • Relaxed manner
  • Clear instructions

  • Attentive
  • Active listening
Explanation of situation to patient

  • Explains Dr. Harvey has not done this before
  • That you will be supervising

  • For Dr. Harvey to do procedure
  • For procedure itself
    • Reason for procedure
    • Procedure explained
    • Risks
    • benefits

  • sitting up in bed, relaxed position, legs apart
  • knee may be extended or flexed 15-20° (more common, opens joint)
  • clean area

  • anteromedial approach described in Roberts and Hedges
  • can be any reasonable approach under patella
Sterile field

  • wash hands and glove
  • sterile instrument filed
  • wash knee with antiseptic
  • sterile drapes
Local anaesthetic

  • appropriate dose and type of LA used
  • applied to the skin +/- the tract of the needle
Needle insertion

  • 18 or 20 G needle/catheter
  • Needle/catheter parallel to bed
  • Direct under patella
  • Can lift patella to aid

  • Small amount for diagnostic purposes
  • Can draw more for comfort
  • Can use 3 way stop-cock or change syringes
  • Can by up to 70 ml in knee joint

  • Into sterile container
  • For m/c/s & gram stain & crystals
  • +/- lactate, glucose, protein
Need 4/5 to pass

  • Communication
  • Supervision
  • Consent
  • Sterile technique
  • Reasonable procedure technique (at least explained, does not have to be completed in the time)

Author: J Haire

Ref: Roberts and Hedges p. 1085-92 

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