Arthrocentesis, Shoulder

Article Author:
Seth Baruffi
Article Editor:
Steve Bhimji
7/17/2018 9:07:00 PM
PubMed Link:
Arthrocentesis, Shoulder


Shoulder arthrocentesis is a necessary and practical skill in the hands of emergency physicians, surgeons, medical specialists and primary care providers alike. It is a useful procedure for both diagnostic and therapeutic indications and has very few contraindications. It is part of the initial evaluation for the exclusion of infection in monoarticular arthritis of unclear etiology. It can be used in rheumatologic and traumatic causes differentiating between gout and pseudogout and hemarthroses. Therapeutically, it can be used to drain symptomatic effusions or hemarthroses as well as to inject steroid or local anesthetic both for pain relief and to facilitate shoulder reduction in an awake patient, reducing the need for procedural sedation and IV pain medication.


To prevent complications, the clinician should be familiar with the shoulder anatomy.

The humeral head and the glenoid fossa of the scapula form the glenohumeral joint of the shoulder. The entire joint is associated with the acromion. Just under the deltoid muscle lies the subdeltoid bursa and may extend to the superior and lateral aspect of the proximal humerus. Medial to the axilla lies the neurovascular bundle.


Diagnostic Indications

  • Diagnosis of infectious or crystalline arthritis
  • Diagnosis of traumatic injury (bony or ligamentous)
  • Determination of communication between a laceration and a joint space

Therapeutic Indications

  • Installation of steroid
  • Installation of local anesthetic
  • Relief of symptomatic, distended effusion
  • Relief of hemarthroses to prevent synovial hypertrophy and fibrosis


The only absolute contraindication to the procedure is cellulitis overlying the entry point; however, known bacteremia is a relative risk as this procedure in the bacteremic patient could theoretically seed the joint space. High suspicion for bacterial joint infection should prompt synovial fluid analysis even in the bacteremic patient as the risks of improper or incomplete treatment of a septic joint far outweigh the theoretical risk of seeding the joint with bacteria. Another relative contraindication is a bleeding disorder or anticoagulant therapy as this could introduce hemarthroses; however, this risk is low compared to risks associated with bacterial joint infection. Prosthetic joints are considered to be a relative contraindication by some outside of a sterile, surgical environment. However, emergent arthrocentesis may be required if a sterile OR environment is not available.



Aseptic Skin Preparation

  • Sterile gloves
  • Iodine solution or chlorhexidine skin prep
  • Sterile gauze pads
  • Sterile, fenestrated drape


  • 25G or 27 G for anesthetic and steroid injection
  • 20-22 G for aspiration (depending on viscosity fluid to be aspirated)

Luer-Lok Syringes

  • 3-5 mL for injection
  • 5-20 mL for aspiration


  • Anesthetic: Lidocaine 1% or Bupivacaine 0.5% (shoulder will accommodate 3-5 mL)
  • Steroid: Methylprednisolone acetate (Depo Medrol) 40 mg or Triamcinolone acetonide (Kenalog) 40 mg

Testing Equipment

Specimen collection tubes

  • Hematology tube for cell count and differential
  • Sterile tube for Gram stain, culture, and smear
  • Heparinized tube for crystal analysis


As with any medical procedure, the keys to success often lie in thorough preparation. Since there are no hyperacute indications for arthrocentesis of the shoulder, adequate preparation time should always be taken to maximize success and to minimize risk.



  • The skin overlying the area of injection can be anesthetized with localized infiltration of 1% lidocaine and a high gauge needle. Alternatively, rapidly evaporating coolants such as ethyl chloride work to provide short-acting anesthesia of the skin at the point of injection. These techniques can be used in combination to anesthetize the skin and underlying soft tissue in increase the comfort of the procedure.


  • The patient should be seated upright with affected arm relaxed preferrably in a chair with armrests or on a stretcher with the head of bed elevated and guardrails up, if possible, as this leaves the patient in a comfortable position, fully exposes the glenohumeral joint, and prevents falls during any potential vaso-vagal syncopal episodes.

Technique: Anterior Approach

After prepping, sterilizing and draping the skin, the most important step in the shoulder arthrocentesis technique is the proper identification of landmarks which will determine the point of entry into the joint. These landmarks include the humeral head, distal clavicle, and coracoid process. The point of entry is medial to humeral head and inferior/lateral to the coracoid process. Insert needle perpendicular to the skin and into the joint space as depicted in the figure. If you chose to identify your landmarks prior to to the sterilization process, using a skin impression or marking pen at the site of insertion can maintain an accurate position during the prepping and draping of the skin. 

While drawing back on the plunger to check for intra-articular blood or synovial fluid. Once the syringe is filled, a hemostat can be placed on the hub of the needle to facilitate removal of a syringe filled with synovial fluid to be sent for analysis and placement of an additional syringe (if needed) to draw of any additional fluid. This same synringe exchange technique can be used to attach a syringe filled with local anesthetic and or injectable steroid as indicated. The skin is then cleaned, and a bandage is placed.


The most important risk to discuss with the patient is an iatrogenic infection. While this complication is rare (approximately 1/10000), it remains a possibility.

  • Pain
  • Bleeding (from the site and into the joint)
  • Re-accumulation of fluid
  • Damage to surrounding soft tissue (nerves, tendons, etc.)
  • Damage to bone or cartilage
  • Failure to obtain fluid (dry tap).

Clinical Significance

Joint Fluid Analysis

  • Characteristics of normal synovial fluid analysis include clear appearance, WBC count less than 200 cells/microL, PMNs less than 25%, synovial lactate less than 5.6 mmol/L, and glucose levels approximating serum glucose.
  • Characteristics of synovial fluid analysis in inflammatory conditions (e.g., osteoarthritis, trauma) include clear/yellow appearance, WBC count less than 2000 cells/microL, PMNs less than 25%, high viscosity, and glucose level approximating serum glucose.
  • Characteristics of synovial fluid analysis suggestive septic joint include WBC count greater than 50,000 cells/microL (greater than 1,100 in a prosthetic joint) with greater than 90% PMN (greater than 65% in a prosthetic joint). Additional suggestive findings include synovial lactate greater than 5.56 mmol/L and LDH >250.
  • It is important to note that the absence of one or more of these findings does not definitively differentiate reactive and inflammatory arthritis from infection. It is imperative that the gram stain is obtained if there is a suspicion of septic arthritis. If there is an insufficient quantity of synovial fluid to perform all of the recommended testings, Gram stain must be prioritized.

Clinical Pearls

  • Needle trauma can damage cartilaginous structures. Avoid hitting the bone.
  • The thoracoacromial artery lies medial to the coracoid
  • Directing needle slightly superiorly will help to avoid neurovascular structures.
  • Use of ultrasound for joint space identification can increase both procedure safety and success.

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      Contributed by Seth Baruffi, MD