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General Arthrocentesis


Assistant Professor of Emergency Medicine
Assistant Professor of Orthopedics & Sports Medicine
University of Florida College of Medicine – Jacksonville


  • Arthrocentesis is a common, safe procedure used to aspirate joint fluid
  • Most commonly, this is to diagnose or exclude crystal arthropathy or septic arthritis
  • Ultrasound is a useful adjunct for arthrocentesis
Clinical example of knee arthrocentesis with aspiration of yellow or straw tinged synovial fluid.[1]Image courtesy of, “The Knee and Leg”


  • Arthrocentesis is a procedure in which a needle is guided into a joint space for the purpose of aspirating synovial fluid.
  • It can be used diagnostically to evaluate the etiology of the effusion.
    • Causes of joint effusions include trauma (i.e. meniscus, labrum, fracture, etc), inflammatory arthropathies, crystal arthropathies, septic arthritis and osteoarthritis.
  • The other purpose of arthrocentesis is therapeutic.
    • Effused joints are painful and removal of fluid can decrease joint pain.
  • Needle insertion also allows for the opportunity to inject medications (anesthetic, NSAIDS, corticosteroids, regenerative therapies, etc)


  • Crystal Arthropathy
  • Hemarthrosis
  • Septic Arthritis
  • Symptomatic relief
  • Unexplained joint effusion
  • Unexplained monoarthritis


  • Sterile equipment
    • Sterile field
    • Sterile gauze
    • Skin sterilization (chlorhexidine, iodine, etc)
    • Sterile gloves
    • Sterile probe cover
  • Needles
    • Anesthetic 23-27g
    • Small joints 23-25g (finger, hand)
    • Medium joints 21-22g (ankle, elbow, wrist)
    • Large joints 18-20g (shoulder, hip, knee)
  • Syringes
    • 5 – 10 cc (injecting anesthetic)
    • 3 – 5 cc (small joint)
    • 5 – 10 cc (medium joint)
    • 20 – 60 cc (large joint)
  • Local anesthetic
  • Optional
    • Skin marking pen (optional)
    • Specimen tubes (if needed)
    • Ethyl chloride (optional), Does not negatively affect sterile field
    • Injectants as appropriate (corticosteroids, NSAIDS, etc)
  • Ultrasound
    • Ultrasound can be a useful aid to evaluate a joint and determine if there is a joint effusion.
    • The most common probe type will be the linear or superficial probe, which typically has a higher frequency (typically 5-15 MHz) to generate high resolution of superficial structures.
    • For deeper joints such as the shoulder or hip, a lower frequency probe such as the curvilinear or phased array probe should be considered.
    • Non-sterile gel can be used to evaluate the joint. If the ultrasound is used, the provider will need both a sterile probe cover and sterile ultrasound gel.


  • Obtain informed consent
    • Discuss risks and benefits with patient
    • Set expectations about the procedure
  • Patient positioning
    • Place patient in optimum position for the procedure
    • If possible, place in a comfortable position
  • Identify and mark appropriate landmarks
    • We recommend using the pen or cap to ‘mark’ the skin where you intend to inject with an indentation
  • Skin sterilization (chlorhexidine, iodine)
  • Sterile drape
  • Local anesthetic and then anesthetic to deeper tissue along projected path
    • Any anesthetic including lidocaine is ok. It is worth noting one study found methylparaben in lidocaine can decrease sensitivity of synovial fluid culture if lidocaine is included in culture sample[2]Liu K, Ye L, Sun W, Hao L, Luo Y, Chen J. Does use of lidocaine affect culture of synovial fluid obtained to diagnose periprosthetic joint infection (PJI)? An in vitro study. Med Sci Monit. … Continue reading
  • Consider two needle technique (one for anesthetic and one for aspiration)
    • This is particularly important for large joints using a large gauge needle

Additional Considerations

  • Troubleshooting
    • If having trouble aspirating fluid, consider adding ultrasound to improve needle accuracy. Consider using larger needles for aspiration as material may be viscous.
  • Post procedure care
    • Compression of any bleeding
    • Application of bandage
    • Avoidance of exposure to contaminants or submersion in water for a period of time, typically 24-48 hours
  • Risk factors
    • Infection
    • Injury to surrounding nerve, arteries or veins
    • Soft tissue injuries
  • Contraindications
    • No absolute contraindications
    • If concern is high for septic arthritis, the procedure should be performed.
  • Relative contraindications
    • Abnormal or altered anatomy
    • Overlying cellulitis, proceduralist will want to avoid seeding soft tissue infection into joint
    • Coagulopathy
      • Patients on anticoagulation can generally safely undergo arthrocentesis.
      • Can consider using a smaller needle than you typically would.
      • Literature supports safety of procedure on warfarin and NOAC[3]Yui JC, Preskill C, Greenlund LS. Arthrocentesis and joint injection in patients receiving direct oral anticoagulants. Mayo Clin Proc. 2017;92(8):1223-1226.[4]Bashir MA, Ray R, Sarda P, Li S, Corbett S. Determination of a safe INR for joint injections in patients taking warfarin. Ann R Coll Surg Engl. 2015;97(8):589-591.[5]Ahmed I, Gertner E. Safety of arthrocentesis and joint injection in patients receiving anticoagulation at therapeutic levels. Am J Med. 2012;125(3):265-269.
    • Joint prosthesis
    • Acute fracture
    • Osteomyelitis
    • Uncooperative patients
    • Bacteremia
  • Medication Injections
    • Corticosteroid injection can be considered in patients with inflammatory, crystal or osteoarthropathies to help decrease inflammation and improve pain. Corticosteroid injection can be considered on a case by case basis but should be avoided in patients in which infection is a consideration. Additional relative contraindications include uncontrolled diabetes, pending joint surgery, history of arthroplasty, and fracture.
    • Analgesic medications can be injected at the discretion of the physician. Considerations include NSAIDS, Opiates.
    • Other injectants including dextrose, viscosupplementation and regenerative therapies are typically reserved for the outpatient setting.

Pearls & Pitfalls

  • If the patient complains of pain during the procedure, you may pause to inject more local anesthetic. Also consider providing PO, IM or IV medication prior to the procedure depending on their degree of discomfort.
  • Patients with a larger body habitus may be more challenging to aspirate. In these cases, be sure to have staff available to help manipulate soft tissue and have longer needles.
  • Consider having an assistant available to help with either pushing fluid towards the needle tip, holding the probe and/or drawing back on larger syringes that require two hands.