• Skin or soft tissue infection (eg, cellulitis,
septic bursitis) because there is an increased risk of causing a
• Corticosteroid injection into a known or suspected septic joint.
• Coagulopathy. The procedure may result in hemarthrosis, but
one needs to weigh the risk against the need to diagnose a septic
• Bacteremia, because of the increased risk of causing septic joint.
• Syringes (20 mL for knee; 10 mL for ankle).
• 21–25-gauge needles; they must be long enough to enter joint.
• Sterile collection container.
• Povidone-iodine and alcohol for sterile preparation of skin.
• Sterile gloves.
• 4 × 4 gauze.
• Ethyl chloride (optional).
• Lidocaine (optional).
• Infection occurs in < 1/10,000 when
performed under sterile conditions.
• Bleeding into joint is exceedingly rare, even in patients who
are taking anticoagulant medication.
• If corticosteroids are being injected, there is a risk of skin discoloration
and fat atrophy following the procedure.
• Do not make an ink mark directly over injection/aspiration
site because it will enter the joint when the needle passes through
• Instead, use the wood end of a sterile cotton swab or another
round object to make an indentation in the skin prior to cleaning
• If infection is a concern, a larger bore needle (18 gauge or 19
gauge) may be needed to aspirate because sometimes purulent fluid
will not be drawn into a smaller needle.
• Do not overtighten the needle on to the syringe, and check to
make sure the needle easily twists off the syringe before starting
• This allows you to empty a full syringe and reattach it without
ever pulling the needle out of the joint.
• Lidocaine can be used to numb the skin prior to aspiration/injection,
but it can distort anatomic landmarks.
• Alternatively, a topical agent such as ethyl chloride can be used.
• With the knee extended, have the patient relax
• Palpate the superior and lateral edge ...
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