1. Indications for arthrocentesis
    • Diagnostic: Septic arthritis, Hemarthrosis/Traumatic effusion, Crystal-induced arthropathy (Gout, Pseudogout), Unexplained joint effusion or mono-arthritis
    • Therapeutic: provide pain/discomfort relief due to a tense effusion
    • Therapeutic: administer a pharmacologic agent, Steroid injections, Viscosupplementation
  2. Contraindications to intra-articular injection
    • Cellulitis overlying the proposed site for the injection
    • Adjacent osteomyelitis
    • Known or relative bacteremia (although if septic arthritis is suspected, this should not prohibit aspiration for diagnosis)
    • Prosthetic joint – if effusion is in a replaced joint, consult the orthopaedic surgeon –or—impending joint replacement surgery (planned procedure w/in days)
    • Osteochondral fracture
    • Poorly controlled diabetes
    • *** Do not inject any therapeutic agent into a joint found to have a hemarthrosis (aspiration is appropriate)
    • Relative contraindication: known coagulopathy or anti-coagulated state
  3. Normal Synovial Fluid Findings
    • Appearance: clear yellow, amber
    • Viscosity: high
    • Special Findings: none
  4. Traumatic Synovial Fluid Findings
    • Appearance: straw to red
    • Viscosity: high
    • Special Findings: blood may be ++
  5. OA Synovial Fluid Findings
    • Appearance: clear yellow
    • Viscosity: high
    • Special Findings: cartilage fragments
  6. Gout Synovial Fluid Findings
    • Appearance: cloudy
    • Viscosity: decreased
    • Special Findings: monosodium urate crystals (needle-like shape)
  7. RA Synovial Fluid Findings
    • Appearance: greenish, cloudy
    • Viscosity: low
    • Special Findings: latex RA, hemaglutination titer, or sheep-cell agglutination test
  8. Septic Arthritis Synovial Fluid Findings
    • Appearance: turbid to purulent
    • Viscosity: low
    • Special Findings: positive culture
  9. TB Arthritis Synovial Fluid Findings
    • Appearance: cloudy
    • Viscosity: low
    • Special Findings: positive culture for acid-fast bacillus
  10. Arthrocentesis Procedure
    • 1.Examine the knee joint. You may observe a supra-patellar bulge, the hollows of the knee around the medial & lateral patellar border disappear. Palpate for temperature
    • 2.If you determine that aspiration and/or injection is an appropriate intervention. Place the patient in a comfortable position on the exam table with their knee in full extension or slightly flexed to no greater than 15◦(results in a relaxed quadriceps & patellar tendon). Obtain informed consent for the procedure!
    • 3.Palpate the bony margin of the patella medially & laterally (you may choose to either side based on your comfort & preference based on the clinical exam)
    • 4.Optimal location to enter the joint space is ~1cm medially or laterally from the superior 1/3 of the patellar border (you may mark the site if you prefer)
    • 5.Prepare the site. Cleanse the site with antiseptic solution and you may choose to use a sterile drape to isolate the field
    • 6.Anesthetize the superficial skin with 1% lidocaine and then proceed to administer ~5-10cc of 1% lidocaine deeper along the trajectory of the arthrocentesis needle
    • 7.Identify your bony landmarks again (the medial or lateral patellar border)
    • 8.Insert an 18 gauge syringe posterior to the patella (the needle should not come in contact with the bone)
    • 9.Constantly pull back on the plunger as you advance the needle until you begin to collect synovial fluid in the syringe
    • 10.You may need to remove the 1st syringe from your needle (while leaving the needle in place) & attach a 2nd syringe if the volume of the effusion is large. Use your non-dominant hand to compress the opposite side of the joint if needed
    • 11.Once you observe decreased flow of synovial fluid into your syringe and are able to see the hollows of the knee around the medial & lateral patella – gently remove the syringe & arthrocentesis needle. Cleanse the area & place a bandage over the injection site
    • 12.Place the used needles in the biohazard receptacles’ for sharps
    • 13.You should note the appearance of the fluid in your office visit notes & on any lab request form
    • 14.Depending on the suspected diagnosis – you will fill an: EDTA tube (purple top) – for cell count & differential, Sodium/heparin tube (green top) – for crystal examination, Leaving at least 5cc for culture & gram stain (usually placed in a red top tube)
  11. Injection
    • If you are planning to inject a therapeutic agent following the arthrocentesis – follow the same steps #1-9 above & then
    • 10. While the needle remains in place (you can use a hemostat on the hub of the needle to stabilize it but DO NOT touch the needle tip against joint surfaces when you remove the syringe) attach a syringe filled with corticosteroid and gently empty into the joint space
    • - Proceed with steps #11-14 from above
  12. Therapeutic choices:
    • Corticosteroids: Celestone, 6mg/mL – use 1 mL mixed with 3-5mL of 1% lidocaine. Depo-medrol 40mg/mL – use 1 mL mixed with 3-5mL of 1% lidocaine.
    • Viscosupplementation: Hyalgan, Orthovisc, and Synvisc
    • Generally not a primary care procedure – performed in orthopeadic & rheumatology practices
  13. Potential Complications:
    • Iatrogenic infection
    • Local trauma
    • Pain
    • Reaccumulation of effusion
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