Arthrocentesis: Knee (Emergency Medicine)

• Diagnostic evaluation of acute monoarticular or polyarticular arthritis
• Therapeutic treatment of acute joint effusions

• Overlying skin infections or lesions
• Arthrocentesis is probably safe in patients with a coagulopathy, unless the coagulopathy is severe. However, the safety of arthrocentesis in patients with abnormal coagulation is not established.
• Bacteremia

• Skin cleansing agent (e.g., chlorhexidine or povidone-iodine)
• Sterile gauze
• Local anesthetic (1% lidocaine is acceptable)
• Small (e.g., 5 mL) syringe with 25-gauge needle for anesthetic injection
• Syringe (30-60 mL for large effusions) with an 18-gauge needle for joint aspiration
• Specimen tubes for submission of synovial fluid to the laboratory; typically, an EDTA tube is used for cell count and differential, and a lithium heparin tube is used for crystal examination.
• Bandage
• Elastic wrap (to be applied after large joint aspirations)
• Gloves

• The knee joint is the largest synovial cavity in the body and extends from the proximal tibia to the suprapatellar region.
• A subcutaneous prepatellar bursa is located on the outer surface of the patella, just under the subcutaneous tissue.
• The needle enters 1 cm medial or lateral to the superior third of the patella.

Figure 2 :  Left knee effusion

View Larger Image

Figure 5 :  Equipment

View Larger Image

Figure 6 :  Knee Anatomy

View Larger Image

The full content of this section includes:

• Step-by-step text instructions for performing the procedure
  
• Clinical pearls providing practical clinical tips from medical experts
• Patient safety guidelines consistent with Joint Commission and OHSA standards
• Links to medical evidence and related procedures

Figure 7 :  Patient positioning

View Larger Image

Figure 9 :  Medial approach to the knee joint

View Larger Image

Figure 10 :  Proper needle placement

View Larger Image

• Monitor for signs of infection in the region.
• Place an elastic bandage around the knee¹⁵
• Treat suspected septic arthritis before formal diagnosis.
  • The choice of antibiotic may be made empirically, or based upon the gram stain results.
  • Intraarticular antibiotics are not recommended.⁵
  • The joint capsule must be repeatedly drained until the effusion is cleared. Operative drainage may be needed.
• Treatment of gout
  • High-dose nonsteroidal antiinflammatory agents, colchicine, and oral steroids may be used.
  • Antihyperuricemia treatment should be delayed.
• Treatment of pseudogout
  • Treatment is identical to that for acute gout. Antihyperuricemic agents are not used.

• Complications are uncommon.
  • Iatrogenic infection
  • Iatrogenic hemorrhage
  • Pain during the procedure
  • Reaccumulation of the joint fluid.