The most important landmark for knee aspiration is the lateral edge of the patella.
1. Start off by identifying the superior pole and lateral edge of the patella (Figure 1).
2. Identify the soft spot approximately 1 cm below the lateral edge of the patella. This is the landmark for aspirating the knee (Figure 2).
3. Lightly hold the patella between the thumb and index finger. The needle should be introduced into the soft spot just under the patella. (Figure 3)
4. There should be no resistance to flow and the patient should be comfortable throughout the procedure. Occasionally the needle may need to be withdrawn or angled slightly to maximize extraction of the effusion or blood.
Frank blood is aspirated from this patients knee suggesting the likelihood of an Anterior Cruciate Ligament tear. (Figure 4).
If there is a clinical suspicion of infection, urgent Gram stain should be requested for and the aspirate should be sent for microscopy and culture.