Background

Arthrocentesis (synovial fluid aspiration) of the knee can be performed either diagnostically (for identification of the etiology of acute arthritis) or therapeutically (for pain relief, drainage of effusion, or injection of medications).^{[1, 2]}

To avoid puncture of tendons, blood vessels, and nerves, the clinician performing the procedure should be familiar with the anatomy of the specific joint. The risk of such injuries can be minimized by using the extensor surface of the joint for needle insertion while keeping the joint in minimal flexion.

Although this approach is not covered in this article, it seems that ultrasound-guided arthrocentesis and injection of the knee are superior to arthrocentesis and injection guided by anatomic landmarks and palpation, resulting in significantly less procedural pain, improved arthrocentesis success, greater synovial fluid yield, more complete joint decompression, and improved clinical outcomes.^[3]

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Indications

Indications for diagnostic knee arthrocentesis include the following:

• Evaluation of monoarticular arthritis
• Evaluation of suspected septic arthritis
• Evaluation of joint effusion
• Identification of intra-articular fracture
• Identification of crystal arthropathy

Indications for therapeutic knee arthrocentesis include the following:

• Relief of pain by aspirating effusion or blood
• Injection of medications (eg, corticosteroids, antibiotics, or anesthetics)
• Drainage of septic effusion

Contraindications

There are no absolute contraindications for knee arthrocentesis. Relative contraindications include the following:

• Cellulitis overlying the joint - If arthrocentesis is performed, the patient should be admitted for the administration of intravenous (IV) antibiotics, even if the synovial fluid is not suggestive of infectious arthritis
• Skin lesion or dermatitis overlying the joint
• Known bacteremia
• Adjacent osteomyelitis
• Uncontrolled coagulopathy
• Joint prosthesis – Preferably, a joint prosthesis is tapped by an orthopedist

Periprocedural Care