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How To Do Knee Arthrocentesis


Alexandra Villa-Forte

, MD, MPH, Cleveland Clinic

Reviewed/Revised Jun 2023
Topic Resources

Arthrocentesis of the knee is the process of puncturing the knee (tibiofemoral and patellofemoral) joint with a needle to withdraw synovial fluid.

Indications for Knee Arthrocentesis

Contraindications to Knee Arthrocentesis

Absolute contraindications

  • Infection of skin or deeper tissues at the anticipated site of needle insertion

If possible, an alternate, uninfected puncture site should be used. However, acutely inflamed joints may be generally warm, tender, and erythematous, thus mimicking extra-articular infection and making it hard to find an uninvolved insertion site. Ultrasonography may be helpful; visualization of a joint effusion by ultrasonography can reinforce the decision to do arthrocentesis despite surrounding erythema. NOTE: If infectious arthritis is strongly suspected, arthrocentesis should be done regardless of erythema or negative ultrasonographic results because joint infection must not be missed.

Relative contraindications

  • Severe bleeding diathesis, which may need to be corrected before arthrocentesis; routine therapeutic anticoagulation is not a contraindication, particularly if infection is suspected

  • Prosthetic joint, which is susceptible to iatrogenic infection; prosthetic joint arthrocentesis should generally be done by an orthopedic surgeon

Complications of Knee Arthrocentesis

Complications are uncommon and include

  • Infection

  • Damage to tendon, nerve, or blood vessels (traumatic tap)

Equipment for Knee Arthrocentesis

  • Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol), sterile gauze, and gloves

  • Nonsterile underpads

  • Local anesthetic (eg, 1% lidocaine, 25- to 30-gauge needle, 3- to 5-mL syringe)

  • For joint aspiration, a 51-mm (2-inch) 18- or 20-gauge needle and 20- to 60-mL syringe

  • For large effusions, multiple syringes, plus either a hemostat or a three-way stopcock, may be needed

  • Appropriate containers for collection of fluid for laboratory tests (eg, cell count, crystals, cultures)

  • For intra-articular therapeutic injection, a syringe containing a corticosteroid (eg, triamcinolone acetonide 20 to 40 mg or methylprednisolone acetate 40 to 80 mg) and/or a long-acting anesthetic (eg, 0.25% bupivacaine), a 23- to 25-gauge needle, and a hemostat to help switch syringes, if needed

Additional Considerations for Knee Arthrocentesis

  • Sterile technique is necessary to prevent microbial contamination of both the joint space and the aspirated synovial fluid.

Relevant Anatomy for Knee Arthrocentesis

  • When using the anteromedial approach, the needle enters 1 to 2 cm medial to the superior half or third of the patella. A similar approach can be used from the lateral side of the knee.

Arthrocentesis of the knee

The knee and connecting suprapatellar pouch can be punctured while the patient is supine and the knee is extended. The needle, 18- or 20-gauge, can be inserted anteromedially, under the cephalad half or third of the patella. Alternatively, the needle can be inserted laterally, just under the cephalad edge of the patella (shown in drawing).

Arthrocentesis of the knee

Positioning for Knee Arthrocentesis

  • Position the patient supine on the stretcher with the knee either extended fully or flexed 15 or 20° with a towel roll under the knee. Align the foot perpendicularly to the floor.

Step-by-Step Description of Knee Arthrocentesis

  • Palpate the knee to identify the patella. If desired, mark the needle insertion site with a skin-marking pen or preferably an indentation (before cleansing the skin).

  • Rest the knee on an underpad. Prepare the site and surrounding area with a skin-cleansing agent, such as chlorhexidine or povidone iodine, then use an alcohol wipe to remove the agent.

  • Place a wheal of local anesthetic over the needle entry site using a 25-gauge needle. Then inject more anesthetic into the deeper tissues along the anticipated trajectory of the arthrocentesis needle, but do not enter the joint space.

  • Aspirate the joint using an 18- or 20-gauge needle on a 20- to 60-mL syringe. If using a three-way stopcock, the stopcock is installed between the needle and the syringe.

  • Enter the skin in a perpendicular fashion and direct the needle posteriorly behind the patella, toward the intercondylar notch. To avoid touching articular cartilage with the needle, try to maintain a horizontal needle trajectory; also, you may grasp the patella and gently pull it upward.

  • Pull back on the plunger gently as the needle is advanced. Synovial fluid will enter the syringe when the capsule is entered. If the needle hits bone, retract almost to the skin surface and then redirect at a different angle. If aspiration is unsuccessful, you can try moving from a position of slight knee flexion to complete extension or try the procedure from the opposite side of the knee.

  • Aspirate as much fluid as possible. Apply gentle pressure to the suprapatellar region to help drain extra fluid.

  • In large effusions, a second syringe may be required. You may leave the needle in place by holding it securely with a hemostat or by using the three-way stopcock during syringe exchanges.

  • If intra-articular medications (eg, anesthetic, corticosteroid) are to be given, hold the hub of the needle motionless (using a hemostat if available) while removing the synovial fluid-containing syringe and replace it with the medication-containing syringe. If the needle has remained in place in the joint space, there will be no resistance to medication injection.

  • After injecting a corticosteroid, move the joint through full range of motion to distribute the medication throughout the joint.

  • After aspiration, remove the needle and cover the site with an adhesive bandage or sterile dressing.

How to do Arthrocentesis of the Knee
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Aftercare for Knee Arthrocentesis

  • Ice, elevation, and oral nonsteroidal anti-inflammatory drugs (NSAIDs) may help relieve pain.

  • With large effusions, apply an elastic bandage after the procedure to help limit swelling and pain.

  • If intra-articular anesthetic has been given, limited joint activity should be prescribed for 4 to 8 hours. Weight-bearing joints, such as the knee or ankle, may be especially prone to injury after anesthetization.

  • If an intra-articular corticosteroid has been given, the joint should be rested for about 24 to 48 hours.

  • If the patient has increased erythema, pain, and/or swelling > 12 hours after the procedure, the joint should be examined for possible infection.

Warnings and Common Errors for Knee Arthrocentesis

  • Carefully ensure optimal positioning before joint puncture.

  • Allow adequate time for local anesthesia to take effect before proceeding.

  • To avoid damaging the synovium and articular cartilage, do not advance the needle against resistance and do not move the needle once it has begun draining synovial fluid.

  • If the needle tip must be relocated, first withdraw it almost to the skin surface and then redirect; do not try to change the angle of insertion while a needle is embedded in tissue.

  • Distinguish a knee effusion from effusion or swelling of the prepatellar bursa.

Tips and Tricks for Knee Arthrocentesis

Consider doing ultrasonography if there is no obvious large effusion.

Additional fluid can sometimes be aspirated by applying pressure to the suprapatellar pouch and then to the popliteal space while aspirating.

Note also that warmth, tenderness, and erythema may overlie an acutely inflamed arthritic joint, mimicking extra-articular infection.

  • Joint effusion

  • Circumferential joint pain and capsule tenderness

  • Pain with both gentle, passive motion and with active joint motion

When inspecting fluid, consider the following:

  • The hemarthrosis of a traumatic tap tends to be nonuniformly bloody and tends to clot.

  • Fat within a hemarthrosis (lipohemarthrosis) is caused by an occult fracture.

Drugs Mentioned In This Article

Drug Name Select Trade
Betasept, Chlorostat, DYNA-HEX, Hibiclens, Oro Clense , Peridex, Periogard, PerioRx , Perisol
7T Lido, Akten , ALOCANE, ANASTIA, AneCream, Anestacon, Aspercreme with Lidocaine, AsperFlex, Astero , BenGay, Blue Tube, Blue-Emu, CidalEaze, DermacinRx Lidocan III, DermacinRx Lidogel, DermacinRx Lidorex, DERMALID, Dologesic, Ela-Max, GEN7T, Glydo, Gold Bond, LidaFlex, LidaMantle, Lido King Maximum Strength, Lidocan, Lidocare, Lidoderm, LidoDose, LidoDose Pediatric, Lidofore, LidoHeal-90, LIDO-K , LidoLite, Lidomar , Lidomark, LidoPure, LidoReal-30, LidoRx, Lidosense 4 , Lidosense 5, Lidosol, Lidosol-50, LIDO-SORB, Lidotral, Lidovix L, LIDOZION, Lidozo, LMX 4, LMX 4 with Tegaderm, LMX 5, LTA, Lubricaine For Her, Lydexa, Moxicaine, Numbonex, ReadySharp Lidocaine, RectaSmoothe, RectiCare, Salonpas Lidocaine, Senatec, Solarcaine, SUN BURNT PLUS, Tranzarel, Xyliderm, Xylocaine, Xylocaine Dental, Xylocaine in Dextrose, Xylocaine MPF, Xylocaine Topical, Xylocaine Topical Jelly, Xylocaine Topical Solution, Xylocaine Viscous, Zilactin-L, Zingo, Zionodi, ZTlido
Aristocort, Aristocort A, Aristocort Forte, Aristocort HP, Aristo-Pak, Aristospan, Azmacort, Children's Nasacort Allergy 24HR Nasal Spray, Cinalog, Cinolar, Flutex, Hexatrione, Kenalog, Kenalog in Orabase, Kenalog-10, Kenalog-40, Kenalog-80, Nasacort, Nasacort AQ, Oralone, SP Rx 228 , Tac-3 , Triacet , Triamonide , Trianex , Triderm , Triesence, XIPERE, Zilretta
A-Methapred, Depmedalone-40, Depmedalone-80 , Depo-Medrol, Medrol, Medrol Dosepak, Solu-Medrol
Marcaine, Marcaine Spinal, POSIMIR, Sensorcaine, Sensorcaine MPF , Xaracoll
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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