Relative contraindications 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 generally be done by an orthopedic surgeon Complications of Shoulder Arthrocentesis Complications are uncommon and include Infection Damage to tendon, nerve, or blood vessels (traumatic tap) Equipment for Shoulder Arthrocentesis Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol), sterile gauze, and gloves Nonsterile pads Local anesthetic (eg, 1% lidocaine, 25-gauge needle, 3 - to 5-mL syringe) For joint aspiration, a 51-mm (2-inch) 20-gauge needle and 20-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), a 22-gauge needle, and a hemostat to help switch syringes, if needed Additional Considerations for Shoulder Arthrocentesis Sterile technique is necessary to prevent microbial contamination of both the joint space and the aspirated synovial fluid.