Aspiration of a knee effusion

The lateral parapatellar approach is preferred in certain scenarios, including when patients are overweight or obese, the medial approach has failed, and/or when ultrasound has demonstrated a full lateral gutter. The lateral approach is preferred since the synovial cavity distends laterally in 75% of patients. Landmarks include the lateral patella, superior patellar pole, and the iliotibial band. A 1.5 inch (4 cm) 22-gauge needle is inserted at an angle of approximately 70 degrees, halfway between the undersurface of the patella and the middle of the iliotibial band. One mL of local anesthetic is placed in the lateral retinaculum and intraarticularly. The needle is advanced to a depth of 1.5 to 3 inches (4 to 8 cm) and joint fluid is aspirated.