Clinical landmarks can let you down! As this video shows, use ultrasound to both positively identify a knee joint effusion more successfully than clinical examination and to locate the easiest pocket for arthrocentesis and/or injection where classic landmarks would have failed.
this is a scan with a linear transducer in a longitudinal orientation placed right at the knee joint here's the femur here's the tibia and what's immediately apparent in this patient with a swollen and painful knee is that there's no obvious fluid right at the side of the traditional arthrocentesis area at the lateral aspect of the joint itself now when we take the probe and we start sliding up proximal the femur we'll see a significant fluid collection identified here here's the femur again and now we see a large fluid hypoechoic structure that's outside of the joint but this area is actually the suprapatellar bursa that is extending both medially and laterally on this patient consistent with actually a significant joint diffusion that would have likely been missed if the needle was inserted for an arthrocentesis right at the joint space and then we can further take that probe and rotate transverse where now we have the femur here and this is the suprapatellar bursa and transverse here's the quadriceps tendon superficial to it and in the ultrasound guided arthrocentesis approach we would come in in plane underneath that quadricep tendon coming into the suprapatellar bursa and this is basically would be a very successful arthrocentesis where as if we had gone in the traditional anatomic landmark we would have missed entirely
