• 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 Indications

  • Therapeutic (decrease intra-articular pressure, injection of anesthetics/steroids)


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

Equipment Needed

  • 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


  • 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 18ga needle (for larger joints) 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



Shoulder arthrocentesis
  • Anterior approach
    • Sit patient upright facing you
    • Insert needle just lateral to coracoid process (between coracoid process and humeral head)
    • Direct needle posteriorly
  • Posterior Approach
    • Sit patient upright with back facing you
    • Palpate scapular spine to its lateral limit (the acromion)
    • Identify the posterolateral corner of the acromion
    • Insert 1.5-in needle 1 cm inferior and 1 cm medial to this corner
    • Direct needle anterior and medial toward presumed position of coracoid process
    • Glenohumeral joint is located at a depth of approximately 1-1.5in


  • Place elbow in 90o flexion, resting on a table, with hand prone
  • Locate radial head, lateral epicondyle, and lateral aspect of olecranon tip
    • These landmarks form the anconeus triangle
  • Palpate a sulcus just proximal to the radial head (in the middle of the triangle)
  • Insert needle into sulcus directed medial and perpendicular to radius toward distal end of antecubital fossa


Wrist arthrocentesis
  • Palpate landmarks with wrist in neutral position:
    • Radial tubercle of distal radius
    • Anatomic snuffbox
    • Extensor pollicis longus tendon
    • Common extensor tendon of index finger
  • Insert needle perpendicular to skin, ulnar to radial tubercle and anatomic snuffbox, between extensor pollicis longus and common extensor tendons


  • Can be entered medially or laterally to the patella, superior or inferior to patella
  • Fully extend knee and ensure quadriceps muscle is relaxed (optionally bump with 20 deg of flexion)
    • Place your thumb on the patella and slide it over as you enter with needle
    • For Suprapatellar Approach 1 cm lateral and 1 cm superior
  • Identify midpoint of patella; insert needle either 1 cm lateral or medial
  • Direct needle posterior to patella and horizontally toward the joint space
  • Compression or "milking" applied to both sides of joint space may facilitate aspiration


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


  • Should only be done under ultrasound guidance
  • Orient your probe along the axis of the femoral neck (indicator towards abdomen)
  • Identify Landmarks (Femoral V/A/N, Acetabular Labrum, Femoral Head/Neck)
  • Effusion will be seen between femoral head/neck and the iliopsoas muscle
  • Insert needle under probe, making sure that you know where patient's femoral V/A/N are


  • Have palm facing down and apply gentle traction to the affected digit
  • Insert needle dorsally just medial or lateral to midline and proximal to the base of the proximal phalanx


  • Have palm facing down and apply gentle traction to the affected digit
  • Insert needle dorsally medial or lateral to midline and proximal to base of middle or distal phalanx


  • Patient supine with flexion of the MTP joint 15-20 degrees and apply gentle traction
  • Insert needle dorsally just medial or lateral to midline between the metatarsal head and base of proximal phalanx


  • Patient supine with joint flexed 15-20 degrees with gentle traction
  • Insert needle dorsally, medial or lateral to midline between head of proximal phalanx and base of more distal phalanx


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


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)


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[2]

See Also

External Links


  1. *Freeman, K., A. Dewitz, et al. (2007). "Ultrasound-guided hip arthrocentesis in the ED." Am J Emerg Med 25(1): 80-86.
  2. 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.