Arthrocentesis: ankle

Overview

Medial approach: enter space between anterior border of the medial malleolus and the tibialis anterior tendon
Medial approach: have patient lie supine, and plantar flex the ankle so the angle is close to 90 degrees.

Indications

General arthrocentesis indications

  • Suspicion of septic arthritis
  • Suspicion of crystal induced arthritis
  • Evaluation of therapeutic response for septic arthritis
  • Unexplained arthritis with synovial effusion
  • Evaluation of joint capsule integrity if overlying laceration
  • Relative: therapeutic (decrease intra-articular pressure, injection of anesthetics/steroids)

Contraindications

General arthrocentesis contraindications

  • No absolute contraindications for diagnostic arthrocentesis
  • Do not inject steroids into a joint that you suspect is already infected
  • Relative Contraindications:

Equipment Needed

General arthrocentesis equipment

  • Betadine or Chlorhexadine
  • Sterile gloves/drape
  • Sterile gauze
  • Lidocaine
  • Syringes
    • Small syringe (6-12cc) for injection of local anesthetic
    • Large syringe (one 60cc or two 30cc) for aspiration
  • Needles
    • 18 gauge: knee
    • 20 gauge: most other joints
    • 25 gauge: MTP joints
    • 27 gauge for anesthetic injection
  • Collection tubes (red top and purple for crystal analysis)
  • Culture bottles
  • Consider utilizing U/S to assess for effusion

Procedure

Lateral and medial ankle arthrocentesis approaches

General Setup

  • Prep area with betadine or chlorhexadine using circular motion moving away from joint x 3
  • Drape joint in sterile fashion
  • Inject lidocaine with 25-30ga needle superficially and then into deeper tissues
  • Insert 20ga needle into joint space while pulling back on syringe
  • Stop once you aspirate fluid; aspirate as much fluid as possible
    • Send: cell count, culture, Gram Stain, crystal analysis

Medial approach (tibiotalar)

  • Have patient supine with foot perpendicular to leg
  • Palpate sulcus lateral to medial malleolus and medial to TA and EHL tendons
  • Then plantarflex foot with needle entering skin overlying the sulcus
  • Angle needle slightly cephalad as it passes between medial malleolus and TA tendon

Lateral approach (subtalar)

  • Keep foot perpendicular to leg
  • Enter subtalar joint just below tip of lateral malleolus
  • Direct needle medially toward joint space

Ultrasound Guided

Axial view of TA tendon and EHL tendon (locate also anterior tibial artery, and deep fibular nerve).

Evaluation

Arthrocentesis of synoval fluid

Synovium Normal Noninflammatory Inflammatory Septic
Clarity Transparent Transparent Cloudy Cloudy
Color Clear Yellow Yellow Yellow
WBC <200 <200-2000 200-50,000

>1,100 (prosthetic joint)

>25,000; LR=2.9

>50,000; LR=7.7

>100,000; LR=28

PMN <25% <25% >50%

>64% (prosthetic joint)

>90%

Culture Neg Neg Neg >50% positive
Lactate <5.6 mmol/L <5.6 mmol/L <5.6 mmol/L >5.6 mmol/L
LDH <250 <250 <250 >250
Crystals None None Multiple or none None
  • Viscosity of synovial fluid may actually be decreased in inflammatory or infectious etiologies, as hyaluronic acid concentrations decrease
  • The presence of crystals does not rule out septic arthritis; however, the diagnosis is highly unlikely with synovial WBC < 50,000[1]

Complications

General arthrocentesis complications

  • Pain
  • Infection
  • Re-accumulation of effusion
  • Damage to tendons, nerves, or blood vessels

See Also

External Links

References

  1. Shah K, Spear J, Nathanson LA, Mccauley J, Edlow JA. Does the presence of crystal arthritis rule out septic arthritis?. J Emerg Med. 2007;32(1):23-6.