Cleanse the area to be punctured circumferentially with antiseptic solution Use a 25- or 27-gauge needle attached to a 3-mL syringe to inject 1% lidocaine into the skin and subcutaneous tissues to achieve local anesthesia or, alternatively, spray ethyl chloride topically Avoid injecting into the joint space prior to obtaining fluid for testing and culture FIGURE 130.44 Arthrocentesis of the knee joint Wearing sterile gloves, attach an 18-gauge needle to a 10-mL syringe Hold the syringe in one hand while palpating the lateral margin of the patella with the other Puncture the skin with the syringe held 10 to 20 degrees above the horizontal at the anesthetized site Advance the needle, applying suction on the plunger of the syringe, until it passes into the joint space near the margin of the patella When the joint space is entered, the syringe will fill with synovial fluid Stabilize the syringe by placing the heel of the hand against the patient’s leg during the aspiration Move the needle gently in varied directions to effectively evacuate the joint being careful to minimize the risk of injury to the synovium and cartilage At completion, remove the needle and apply a sterile gauze pad over the puncture site Send the aspirate for the appropriate studies TOPICAL ANESTHESIA AND DIRECT WOUND INFILTRATION