Knee Arthocentesis

A 70 yo patient presents to the emergency department with a painful swollen knee. There has been no trauma and he is systemically well. The decision is made to perform arthrocentesis of the knee joint.

The Procedure:

• I prefer to use the parapatellar approach. Other approaches are available, however I explain why I use this approach in the video below.
• The following is performed with a sterile technique.
• Prepare the skin with sterile solution, allow to dry.
• Drape the area
• Apply local anaesthetic to the skin in the area where the needle is to be inserted into the knee joint.
• Take a 60 mL syringe, although a 20mL syringe will work as well. Attach an 14G or 18G needle.
• Identify the landmarks:
  • Locate the midpoint of either the medial(my preferred technique, the reason explained in the video below) or the lateral border of the patella.
• Insert needle below the midpoint in a direction perpendicular to the skin pointing towards the intercondylar notch of the femur. A rolled towel under the knee can result in a slight flexion of the joint, which may facilitate needle entry into the joint.
  • Aspirate until synovial fluid is extracted. This usually occurs at about 1-2 cm.
  • Aim to not walk the needle along the bone. If bone is encountered, withdraw the needle and gently reinsert.
• Once the procedure is complete, place a sterile bandage over the area.

View the video of the procedure below.