Ultrasound of the nerves of the knee region: Technique of examination and normal US appearance.

The diagnosis of disorders of the peripheral nerves (PN) has traditionally been based on clinical and electrophysiological data since nerve tissue cannot be visualized on standard radiographs. More recently, however, nerve structures have been evaluated with magnetic resonance imaging (MRI) and ultrasound (US). The former modality is expensive and not available in all institutions. There are also some contraindications to its use, and the assessment of long nerves can be time-consuming since different coils must be used. Thanks to recent advances in sonographic software and hardware, US can now be used for in-depth assessment of the PN of the upper and lower limbs.Most knee disorders involve lesions to the cruciate ligaments and/or the menisci, which are difficult to evaluate with US. However, similar symptoms may be caused by compression of one or more nerves in the knee region or intrinsic disorders involving these structures. Because of their superficial positions, the nerves around the knee can be clearly visualized with US. A thorough knowledge of the normal anatomy of this region and a careful scanning technique are essential for a successful diagnostic US examination. In this article, we will review the normal gross and microscopic anatomy of the nerves in the knee region, the US technique used for their examination, and their normal US appearance.