Arthrocentesis and intraarticular injection

Arthrocentesis is a procedure involving the removal of fluid from a joint, most commonly the knee or shoulder. It can be used to diagnose conditions such as septic arthritis and crystal-induced arthropathy, and can provide therapeutic relief (e.g., in hemarthrosis). Intraarticular injection is a related procedure that involves the instillation of therapeutic agents (e.g., glucocorticoids, local anesthetics, platelet-rich plasma), with or without concurrent aspiration, for the treatment of chronic conditions such as arthritis. Relative contraindications for both procedures include bleeding diatheses and overlying cellulitis. To perform aspiration or injection, a needle is inserted into the joint space, guided by landmarks, using a sterile technique; ultrasound may be used as an adjunct. Complications include hemarthrosis and soft tissue injury.

• Arthrocentesis: a procedure involving the aspiration of synovial fluid from the joint space
• Intraarticular injection: a therapeutic procedure for the instillation of medications (e.g., glucocorticoids) or other agents (e.g., platelet-rich plasma) into the joint space

Diagnostic ^[1][2]

• Monoarticular joint swelling of unknown cause
• Symptoms suggestive of:
  • Septic arthritis
  • Crystal-induced arthropathy
  • Inflammatory conditions
  • Intraarticular fracture
• Violation of the joint capsule: assessed using saline arthrography ^[1]

Therapeutic ^[1][2]

• Hemarthrosis or other large effusion: to relieve pressure
• Inflammatory conditions (e.g., arthritis, gout): for intraarticular injection of medications

Do not inject glucocorticoids into a swollen joint if infection has not been ruled out. ^[1]

• Absolute: none ^[2]
• Relative ^[1][2]
  • Overlying cellulitis ^[3]
  • Known bacteremia
  • Bleeding diatheses
  • Prosthetic joint

Only perform arthrocentesis on prosthetic joints if infection is suspected, as prosthetics are at high risk for infection. ^[1]

We list the most important contraindications. The selection is not exhaustive.

Equipment sizing ^[1]

• Needle size
  • Typically 18 to 22-gauge; determined by the anticipated viscosity of the liquid to be aspirated ^[2]
  • Length: Consider the depth of soft tissue overlying the affected joint. ^[2]
• Syringe size
  • Based on the size of the joint and the amount of fluid return expected
  • A 60-mL syringe is often used for therapeutic decompression of large joints, such as the knee.

Agents for intraarticular injection ^[1][4]

Synergistic and compatible agents can be combined in the same injection (e.g., triamcinolone plus lidocaine). ^[5]

• Glucocorticoids: e.g., triamcinolone, methylprednisolone, dexamethasone
• Local anesthetic agents: e.g., lidocaine, bupivacaine
• Others: hyaluronic acid, platelet-rich plasma ^[6]

Ultrasound ^[1][4]

• Helpful adjunct to distinguish between superficial bursitis and intraarticular effusion
• Can help with planning (an anechoic fluid collection confirms effusion) and visualizing the needle position during the procedure
• Use a high-frequency linear probe for maximum resolution; see “Musculoskeletal POCUS” for general technical guidance.
• For joint-specific probe placement and findings, see “Landmarks and positioning.”

Special considerations

• Hip arthrocentesis is typically performed by an orthopedic surgeon under radiological guidance. ^[7]
• Small joints (e.g., in the finger, hand, or foot) may be difficult to aspirate; empiric treatment is often required. ^[1]

If clinical features are equivocal or landmarks are obscured, use point-of-care ultrasound to assess the fluid in the joint space. ^[1]

Knee, parapatellar approach ^[1][2]

• Position: knee in maximum extension or flexed at 15–20°; foot perpendicular to the floor
• Landmarks
  • Can be approached from either the medial or lateral side
  • The medial parapatellar region is thought to be the easiest site to access. ^[2]
• Trajectory
  • Insert the needle 1 cm either medial or lateral to the midpoint of the anterior patellar edge.
  • Direct the needle between the intercondylar femoral notch and the posterior surface.
• Ultrasound probe placement
  • Place the linear probe over the anterior knee (longitudinal orientation).
  • Identify the patella (echogenic object with shadowing).
  • Move the probe medially and laterally to visualize the joint space under the patella.

Shoulder, anterior approach ^[1]

• Position: patient seated upright with the affected arm at the side
• Landmarks
  • Medially: coracoid process
  • Laterally: humeral head
• Trajectory
  • Insert the needle inferior and lateral to the coracoid process.
  • Direct the needle posteriorly.
• Ultrasound probe placement
  • Place the linear probe on the shoulder over the approximate location of the biceps tendon (transverse orientation).
  • If effusion is present, the tendon will be surrounded by anechoic fluid.

Shoulder, posterior approach ^[2]

• Position: patient seated upright with the hand of the affected arm on the opposite shoulder
• Landmarks
  • Posterior border of the acromion
  • Coracoid process
• Trajectory
  • Insert the needle inferior to the posterior border of the acromion.
  • Direct the needle anteriorly and 30° medially.
• Ultrasound probe placement
  • Place the linear probe on the posterior shoulder over the humeral head and the glenoid (transverse orientation).
  • If effusion is present, anechoic fluid will be seen medial to the glenoid.

• Sterile gauze
• Sterile gloves
• Local anesthetic
• 25-gauge or 27-gauge needle (for local anesthesia)
• Antiseptic (e.g., chlorhexidine)
• Appropriately sized syringe (e.g., 60 mL for aspiration of a large joint)
• 18 to 22-gauge needle
• Fluid collection vials (for diagnostic aspiration)
• Ultrasound machine (optional)

Accessing the synovial space

1. Position the patient so that the joint is easily accessible. ^[2]
2. Identify landmarks specific to each joint and the intended entry point (see “Landmarks and positioning”).
3. Confirm the presence of the effusion with ultrasound if indicated.
4. Prep the skin and maintain a sterile field. ^[2]
5. Infiltrate local anesthesia under the skin and along the anticipated needle track.
6. Insert the needle and syringe into the extensor surface of the joint while maintaining traction on the surrounding skin. ^[1]
7. Maintain negative pressure on the syringe during insertion and advance the needle until fluid returns. ^[1]

To minimize pain, avoid repeated contact with the bone when entering the joint space. ^[1]

Arthrocentesis steps ^[1][2]

1. Access the synovial space.
2. Aspirate an adequate amount of fluid for diagnostic testing. ^[2]
3. Manually compress large joints to facilitate additional fluid removal as needed.
4. Transfer fluid to collection vials.
5. Perform intraarticular injection steps, if indicated.
6. Withdraw the needle and apply a dry dressing.

Intraarticular injection steps ^[1][2]

1. Access the synovial space.
2. Perform arthrocentesis steps, if indicated.
3. Apply negative pressure to ensure that the needle is not located intravascularly.
4. Slowly inject the desired agent.
5. Withdraw the needle and apply a dry dressing.

Avoid injection if there is blood flashback suggestive of an intravascular location of the needle.

Aspiration without fluid return ^[1]

• Use ultrasound to visualize the effusion.
• If there is still no fluid return, try an alternative site. ^[2]

Fluid stops flowing during aspiration ^[1]

• Debris or purulent material clogging the lumen of the needle
  • Slightly advance and/or retract the needle.
  • Rotate the needle bevel.
  • Consider a larger needle gauge.
• All fluid removed from the joint : Massage the joint to push any remaining peripheral fluid toward the needle.

• Synovial fluid sent for analysis based on the suspected condition (e.g., septic arthritis, gout)
  • Cell count with differential
  • Gram stain
  • Culture
  • Crystal analysis
  • Additional studies as indicated ^[1]
• Fluid sample visually inspected and characteristics noted (e.g., color and clarity) for documentation
• Procedure documented
• Pain management provided

See “Synovial fluid analysis.”

Arthrocentesis ^[1]

• Infection
• Bleeding and hemarthrosis ^[2]
• Allergic reaction
• Soft tissue injury

Intraarticular glucocorticoid injection ^[1]

• Infection
• Bone necrosis and joint destruction
• Tendon rupture
• Transient facial erythema and diaphoresis
• Transient hyperglycemia
• Steroid flare
• Transient synovitis

We list the most important complications. The selection is not exhaustive.