Arthrocentesis of the knee
From IDWiki
Indications
- Diagnostic: suspected septic arthritis, gout, or hemarthrosis
- Therapeutic: relieve pressure from effusion, remove inflammatory or infected fluid, or steroid injections
Contraindications
- Overlying cellulitis (but can be difficult to distinguish from gout)
- Uncontrolled coagulopathy
- INR > 4
- Platelets <30
- Prosthetic joint: call Orthopedices
- Relatively, suspected bacteremia
Risks
- Bleeding
- Infection
- Pain
Materials
- Gauze, tape, gloves, alcohol wipes
- 25G needle on 5cc syringe for local anaesthetic
- 18-21G needle on 10cc syringe for aspiration
- Lidocaine (1% or 2%)
Procedure
- Positioning
- Supine with knee extended or flexed at 15-20º angle, using a rolled towel under the knee
- Landmarking
- Locate the parapatellar groove medially (or laterally) halfway between the top and bottom of the patella and about 1cm posterior
- Clean the skin
- Inject local anaesthetic, bleb then all the way to the joint
- Insert needle for aspiration perpendicular to ground until you get into the joint space, then aspirate
- If you hit bone, withdraw a bit and try again
- If fluid stops flowing, can try to milk the joint
- Send synovial fluid for:
- Gram stain and culture (sterile urine container)
- CBC (purple-topped CBC tube)
- Microscopy for crystal
