Chapter 54

### Indications

• • Diagnostic: Sampling of fluid for laboratory evaluation (eg, septic joint, inflammatory arthritis).

• Therapeutic.

• • Injection of corticosteroids.

• Injection of local anesthetic.

• Removal of hemarthrosis for pain relief following trauma.

### Contraindications

#### Absolute

• • Skin or soft tissue infection (eg, cellulitis, septic bursitis) because there is an increased risk of causing a septic joint.

• Corticosteroid injection into a known or suspected septic joint.

#### Relative

• • Coagulopathy. The procedure may result in hemarthrosis, but one needs to weigh the risk against the need to diagnose a septic joint.

• Bacteremia, because of the increased risk of causing septic joint.

### Equipment

• • 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).

### Risks

• • 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.

### Pearls and Tips

• • Do not make an ink mark directly over injection/aspiration site because it will enter the joint when the needle passes through it.

• Instead, use the wood end of a sterile cotton swab or another round object to make an indentation in the skin prior to cleaning with povidone-iodine.

• 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 the procedure.

• 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.

### Patient Positioning

• • Have the patient lie supine on the examination table.

• Place the table at a comfortable height for you and sit or stand at the affected side of the patient.

### Anatomy Review

• • The distal femur articulates with the proximal tibia to make up the knee joint.

• The patella sits in a groove anterior to the joint.

### Procedure

#### Knee in Extension

• • With the knee extended, have the patient relax the quadriceps.

• Palpate the superior and lateral edge ...

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