Arthrocentesis
Indications:
- Suspected joint infection
- Note: Ideally remove fluid prior to antibiotic administration.
- Suspected crystal disease (i.e. gout, CPPD).
- Suspected inflammatory joint vs. OA vs. hemarthrosis.
Relative contraindications:
- Local infection over overlying skin
- Needle should never pass through erythematous skin suspected of infection into joint. If there is concern, utilize an alternative approach or consult ortho/rheum.
- Severe coagulopathy.
- If supra-therapeutic INR in patient on warfarin (i.e. INR > 3) may consider delaying arthrocentesis (unless high suspicion of septic joint). This is not an absolute contraindication.
- Note: In most cases, no need to hold antiplatelet, anticoagulant, or warfarin.
Risks of procedure to discuss:
- Rare risks:
- Infection
- Bruising
- Bleeding
- Worsening joint pain
- Extremely rare:
- Allergy to skin preparation or local anesthetic.
- Damage to surrounding tissues/cartilage landmarking helps avoid this
Equipment to obtain:
- Note: All equipment here can be found in the Davies 4 ICU.
- Sterile gloves
- Note: Not needed if using sterile ‘no touch’ technique.
- Chlorhexidine swab x2
- Sterile surgical towels x2
- Anesthetic: 5mL syringe + lidocaine 1% without epinephrine + 25+ gauge needle
- Note: If effusion is large lidocaine may not be required.
- Needle to be inserted + syringes: 10 mL syringe x2 + 22-gauge needle (1.5 inch)
- Needle size anywhere from 18-22 gauge.
- Blunt tip needle x2 (1st used to mark target area, 2nd to draw up lidocaine)
- Towel to support knee
- Note: Only use this if the patient can’t comfortably extend their knee.
- Scissors (if needed to trim hair)
- Specimen container.
- Gauze x2 sterile
- Bandage
Patient preparation
Initial Patient Assessment
- Assess patient for contraindications.
- Have patient supine + knee exposed.
- Identify patella, patellar tendon and regional landmarks.
- Check if the quads are tense – make sure patella is moveable and relaxed (if not relaxed, then entering the joint space may be difficult).
- Note: Knee should be relaxed, not flexed, and pillow should only be used if patient has discomfort with extending the knee while in supine position.
- Note: If the area is extremely hairy can consider removing hair to help landmark and clear area.
- Note: Ultrasound can be used (linear probe, MSK setting) to assess area of largest effusion but is not necessary to find the landmarks of the knee.
Two Main Possible Approaches
- Medial approach:
- Mark the medial area of the patella where needle to be inserted (halfway between superior/inferior margin of patella).
- Palpate and landmark the underside edge of the patella as well.
- Lateral approach
- Retropatellar approach can be used – landmark patella middle to upper third of lateral aspect of patella.
- Lateral superior approach if there is a large effusion: Mark just lateral and superior to the patella.
- Note: Anterior approach is generally not used for aspiration.
Procedural Steps: Standard Lateral Approach
- Position patient supine with knee extended and relaxed
- If patient unable to have comfortable knee extension, can add towel underneath.
- Lateral area of patella marked with blunt tip (as described above).
- Prepare the area with chlorhexidine swabs first +- alcohol swab. Wait till dry.
- Apply surgical towels to patient knee and set up sterile field.
- Note: This is not necessary if sterile no touch technique is followed (see below).
- Put on sterile gloves, drop in lidocaine needle/arthrocentesis needle/5mL syringe/10mL syringes/blunt tip/sterile gauze/bandage into sterile field. Draw up lidocaine.
- Insert lidocaine without epinephrine 1-2 mL into subcutaneous tissue and along eventual tract of needle insertion. Wait 2 minutes for effect.
- May not be required if large effusion is easy to access).
- Insert needle behind under the patella at the landmarked site.
- Draw up fluid sample into syringe.
- For most cases 10 cc is enough to run diagnostic tests but patient will obtain better relief if as much fluid as possible is removed.
- For purulent drainage = can attempt to tap joint dry i.e. 50cc or more.
- Remove needle. Apply sterile gauze with pressure.
- Remove gauze and apply bandage.
- Document procedure.
- Document gross fluid appearance (color, clarity, viscosity) and amount of fluid removed during procedure.
- Place syringe with patient label in specimen bag or specimen container.
- For cell count and diff a min. of 1cc should be inserted to a lavender topped tube.
- For culture a min. of 1cc should be inserted into a red topped tube.
- For crystals 1cc should be inserted in a red topped tube or a tightly closed sterile urine collection container.
- Ensure to note on sample which joint was tapped + whether left or right.
- Put in synovial fluid analyses orders (see below) and ensure sample sent down to lab.
Procedural Steps: Alternative "sterile no touch technique"
- Palpate and landmark medial or lateral target on patient, mark site with connecting end of blunt tip, pen tip etc.
- Clean area well with alcohol/chlorhexidine swabs ensuring landmark is still visible.
- Clean hands well by washing and using hand sanitizer.
- Maintain strict aseptic technique when opening and connecting syringes and needles.
- Don’t set them down on non-sterile surface etc.
- WITHOUT TOUCHING THE LANDMARKED SITE insert needle gently to joint and withdraw plunger while avoiding pushing needle into tissues inadvertently.
- If no fluid is obtained gently adjust the needle tip to ensure it is directed to the supra-patellar pocket and ensure it is in the joint (has entered below patella) Sometimes a slight adjustment will help if tissue is blocking the tip.
- Note: Large knees may be more difficult to enter joint.
- Note: Gentle pressure on the suprapatellar pouch may help force fluid to joint space and into needle.
Post Procedure
- Have patient decrease weightbearing for 24h. Possible cool pack for 20 minutes.
- Synovial fluid samples:
- White blood cell count (cell count and differential)
- < 2000 = non inflammatory i.e. OA
- 2000-50,000 = inflammatory/crystalline (Note: could be infectious if has had some treatment already)
- > 10-30k = possible fungal/mycobacterial.
- > 50k = inflammatory but concerning for bacterial (especially if over 75% PMN) crystals fluid can have fluid numbers similar to infections due to high degree of inflammation.
- Crystal analysis (“non gyne cytology” on lumeo)
- Crystals seen in inflammatory/crystalline arthropathy:
- Negative birefringent needle shape = gout
- Positive birefringent rhomboid = CPPD
- Note: crystals can also be found in those with septic arthritis.
- Gram stain and culture
- White blood cell count (cell count and differential)
Written by: Muralie Vignarajah MD
Staff Reviewed by: Dr. Marie Clements-Baker (Rheumatology) and Dr. Stephen Gauthier (General Internal Medicine)