A Guide to Performing Seated, Foot-On-Floor Position Ultrasound Guided Knee Injections Targeting the Medial & Lateral Parapatellar Bursae & Their Channels

Abstract

Ultrasound guided (USG) supra patellarbursa (SPB)knee aspirations-injections are a current standard practice, typically performed with the patient supine on a plinth, and with the knee flexedto around 30 degrees. This follows research that 30 degrees of knee flexion offers optimal SPB bursal resolution. However,in circumstances of pain-mobility issues affecting plinth transfer, an alternative seated, foot on floor or wheelchair pedal, knee-flexed 90 degrees procedure (SKIF)is proposed. This foot on floor position may facilitate a push-off counter resistance, facilitatingisometric quadriceps contraction enhanced suprapatellar bursa (SPB) viewing, along with improved resolution of thelesser describedmedial-lateral parapatellarbursae(MPPB-LPPB) and their communicating SPB recess channels. As the MPPB-LPPB interconnect to the medial-lateral SPB recesses but are located more superficially and centrifugal to the femoral condyles in areas devoid of underlying articular cartilage, their preferential SKIFinjection-aspiration,mayalso prevent cartilage needle stick injuries.alsoknown as the paracondylar gutters, the relatively superficial MPPB-LPPB position may likewise offer better image resolution, lessenneedle travel distances and needle trajectory re-directs, which may in turn enhance procedure safety, comfort, and speed. Though the medial-lateral SPB recesses have some mention in the literature, it would appear thatinter tri-bursal connecting channels linking the MPPB-LBBP to the SPB recesses have not previously been described.This report explores tri-bursal and inter-bursal channel anatomy, relevant to performing USG SKIF injections and also elucidates the method, potential advantages, and pitfalls of this novel technique.