(See also Evaluation of the Patient with Joint Symptoms Evaluation of the Patient With Joint Symptoms Some musculoskeletal disorders affect primarily the joints, causing arthritis. Others affect primarily the bones (eg, fractures, Paget disease of bone, tumors), muscles or other extra-articular... read more and Evaluation of the Ankle Evaluation of the Ankle An evaluation of the ankle includes a physical examination and sometimes arthrocentesis. (See also Evaluation of the Patient With Joint Symptoms and Overview of Foot and Ankle Disorders.) The... read more .)
Diagnosis of the cause of a synovial effusion (eg, infection Acute Infectious Arthritis Acute infectious arthritis is a joint infection that evolves over hours or days. The infection resides in synovial or periarticular tissues and is usually bacterial—in younger adults, frequently... read more , crystal-induced arthritis Overview of Crystal-Induced Arthritides Arthritis can result from intra-articular deposition of crystals: Monosodium urate Calcium pyrophosphate dihydrate Basic calcium phosphate (apatite) Rarely, others such as calcium oxalate crystals read more )
Removal of a synovial effusion and/or injection of drugs as part of treatment and for pain relief
Infection of skin or deeper tissues at the anticipated site of needle insertion
If possible, an alternate, uninfected site should be used. However, acutely inflamed joints may be generally warm, tender, and red, thus mimicking extra-articular infection and making it hard to find an uninvolved insertion site. Ultrasonography can be done; visualization of a joint effusion 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.
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 be done by an orthopedic surgeon
Complications are uncommon and include
Damage to tendon, nerve, or blood vessels (traumatic tap)
Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol), sterile gauze and bandage, and sterile gloves
Local anesthetic (eg, 1% lidocaine), 25- to 30-gauge needle, 3- to 5-mL syringe)
For joint aspiration, a 25- to 38-mm (1- to 1 1/2-inch) 20-gauge needle and a 10-mL syringe
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 40 mg or methylprednisolone acetate 40 mg) and/or a long-acting anesthetic (eg, 0.25% bupivacaine), and a hemostat to help switch syringes
Sterile technique is necessary to prevent microbial contamination of both the joint space and the aspirated synovial fluid.
Needle insertion is midway between the medial malleolus and the tibialis anterior tendon, over the hollow at the anterior aspect of the malleolus.
Arthrocentesis of the ankle
Synovial fluid is withdrawn from the tibiotalar joint. The patient's foot rests in slight plantar flexion. Needle entry occurs just anterior to the medial malleolus and lateral to the tibialis anterior tendon.
Position the patient supine on the stretcher with the knee bent and the foot in slight plantar flexion, so that the sole of the foot rests on the bed.
Step-by-Step Description of Procedure
Palpate the anterior medial aspect of the ankle joint to identify the medial malleolus and the tibialis anterior tendon. The insertion site is the hollow between this tendon and the anterior edge of the medial malleolus. Ask the patient to dorsiflex the ankle, making the tendon easy to see and palpate. If desired, mark the insertion site with a skin-marking pen or indentation (before cleansing the skin).
Rest the foot on an underpad. Prepare the 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 along the anticipated trajectory of the arthrocentesis needle (about 2 to 3 cm), but do not enter the joint space.
Aspirate the joint using a 20-gauge needle on a 10-mL syringe. Insert the needle perpendicular to the skin, midway between the medial malleolus and the tibialis anterior tendon. Direct the needle posteriorly into the joint space, and pull back gently on the plunger as you advance. Synovial fluid will enter the syringe when the joint is entered.
If the needle hits bone, retract almost to skin surface and then redirect at a different angle.
Drain all fluid from the joint.
If intra-articular drugs (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 drug-containing syringe. If the needle has remained in place in the joint space, there will be no resistance to drug injection.
After injecting a corticosteroid, move the joint through full range of motion to distribute the drug throughout the joint.
Inspect the fluid for blood and fat. Transfer synovial fluid to tubes and other transport media for synovial fluid analysis Synovial fluid examination Some musculoskeletal disorders affect primarily the joints, causing arthritis. Others affect primarily the bones (eg, fractures, Paget disease of bone, tumors), muscles or other extra-articular... read more .
Apply an adhesive bandage or sterile dressing.
Ice, elevation, and oral nonsteroidal anti-inflammatory drugs (NSAIDs) may help relieve 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 ankle or knee, may be especially prone to injury after anesthetization.
If an intra-articular corticosteroid has been given, avoid ankle flexion for 24 to 48 hours. An ankle brace can be used if there is pain after the procedure.
If the patient has increased redness, pain, and/or swelling > 12 hours after the procedure, the joint should be examined for possible infection.
Warnings and Common Errors
Allow adequate time for local anesthesia to take effect before proceeding.
Carefully ensure optimal positioning before joint puncture.
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.
Tips and Tricks
Consider doing ultrasonography if there is no obvious large effusion.
Note also that warmth, tenderness, and redness may overlie an acutely inflamed arthritic joint, mimicking extra-articular infection.
When trying to differentiate infectious arthritis from infection of the overlying structures (a contraindication to arthrocentesis Contraindications Arthrocentesis of the ankle is the process of puncturing the tibiotalar joint with a needle to withdraw synovial fluid. The anteromedial approach is described. (See also Evaluation of the Patient... read more ), infectious arthritis is more likely with the following:
Circumferential joint pain
More pain with passive than active joint motion
When inspecting fluid, consider the following:
The hemarthrosis of a traumatic tap tends to be nonuniformly bloody and tends to clot.