Many of the vascular, bony, and soft tissue structures in the knee can be readily evaluated with point-of-care ultrasound. Point-of-care ultrasound can assist in initial diagnostic evaluation in the setting of direct or indirect traumatic injury to the knee or in undifferentiated knee effusion. The objective of knee ultrasound is to evaluate the normal muscular, ligamentous, cartilaginous, and bony structures of the knee, looking for irregularities in these structures. For atraumatic swollen knees, ultrasound can detect bursitis and can give information regarding the degree of joint effusion. For functional injuries (like those typically related to athletics) or traumatic injuries to the knee, ultrasound can detect a fractured patella or tears of the menisci, medial collateral ligament (MCL), lateral collateral ligament (LCL), patellar tendon, and muscles of the quadriceps. Ultrasound has been found to be more sensitive than radiographs in assessing for lipohemarthrosis, which can be evidence of occult intra-articular knee fracture [1, 2]. For individuals with lower extremity swelling, knee ultrasound can help determine the existence of a Baker’s cyst or deep vein thrombosis. Determining the etiology of knee pain or dysfunction at the bedside may prevent unnecessary imaging, invasive procedures like arthrocentesis, and delay to care. If invasive procedures are needed, however, ultrasound may be used to guide aspiration or therapeutic injection of the knee joint. It is important to note that ultrasound has limited ability to evaluate the deeper ligamentous structures such as the cruciate ligaments, so any clinical suspicion that a patient has further underlying ligamentous damage will warrant further workup with other imaging modalities (Figs. 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 5.10, 5.11, 5.12, 5.13, 5.14 and 5.15).
KeywordsKnee Quadriceps Tendon Patella Bursa