US of the Knee: Scanning Techniques, Pitfalls, and Pathologic Conditions

Abstract

1Pain and other disorders of the knee are a common presenting complaint in the ambulatory setting. Although the cornerstones of imaging evaluation of the knee are radiographs and magnetic resonance (MR) imaging, ultrasonography (US) is less expensive than MR imaging, easily available, and of comparable accuracy in the evaluation of certain pathologic conditions of the knee. The benefits of US include portability, low cost, high spatial resolution, dynamic imaging, and ability to guide percutaneous interventions when indicated. US also allows direct patient contact, facilitating immediate clinical correlation and the ability to compare with the contralateral knee. US evaluation of the knee can be targeted to a specific region on the basis of the complaint or be a comprehensive review. For comprehensive evaluation, the knee is divided into anterior, medial, lateral, and posterior compartments for structured evaluation of the tendons, ligaments, joint space, osseous structures, as well as peripheral nerves and vasculature. US is particularly well suited for evaluating injuries of the quadriceps and patellar tendons, injuries of the medial and lateral collateral ligaments, joint effusions, and fluid collections around the knee. There is additional utility in evaluation of the distal hamstrings tendons, the iliotibial tract, the superficial patellar cortex, the common peroneal nerve, the popliteal vessels, and juxta-articular cystic collections including Baker cyst. In-depth appreciation of relevant sonographic anatomy, common pathologic conditions, knowledge of important pitfalls, and mastery of US technique will allow one to effectively use this powerful bedside tool for the evaluation of a wide variety of knee disorders.

Imaging of Tendons

“…Ultrasound evaluation may be completed with the patient supine, although the posterior structures are better seen in the prone position [19]. Examination may be focused over the area that is relevant to the patient's history; nonetheless a complete examination of all areas should be performed.…”

“…The patient remains supine and rotates hip externally for evaluation of the medial aspect of the knee. The tendinous structures that are evaluated in this region are the pes anserine tendons [19].…”

“…Lateral knee: The patient is in supine position, with internal rotation of the hip, and knee slightly flexed. The key structures that are examined include the iliotibial band, lateral collateral ligament (LCL), biceps femoris tendon, popliteus, common peroneal nerve, and body and anterior horn of the lateral meniscus [19]. The transducer may be initially placed over the long axis of the patellar tendon, and then moved laterally to identify the iliotibial band.…”

Body Mass Index and Segmental Mass Correlation With Elastographic Strain Ratios of the Quadriceps Tendon

“…Quadriceps tendon injuries have a high chance of occurring during routine physical activity, as the tendon is subjected to motorized weight bearing. It has been reported in recent studies that quadriceps tendon injury occurrence is high in men older than 40 years, among athletes who frequently jump, and in patients with systemic inflammatory conditions . Higher tendon injury occurrence among men older than 40 years might be due to areas that lack the capacity to heal impulsively in athletes .…”

“…It has been reported in recent studies that quadriceps tendon injury occurrence is high in men older than 40 years, among athletes who frequently jump, and in patients with systemic inflammatory conditions. 3 Higher tendon injury occurrence among men older than 40 years might be due to areas that lack the capacity to heal impulsively in athletes. 2 Moreover, proinflammatory cytokines are the root cause in patients with the systemic inflammatory conditions.…”