Tendons and nerves represent probably one of the best application of musculoskeletal US due to the high lesion detection rate and accuracy of US combined with its low cost, wide availability, and ease of use. The refinement of high-frequency broadband linear-array transducers, and sensitive color and power Doppler technology, have improved the ability of US to detect fine textural abnormalities of these structures as well as to identify a variety of pathological conditions. Characteristic echotextural patterns, closely resembling the histological ones, are typically depicted in these structures using high US frequencies. In tendon imaging, US can assess dislocations, degenerative changes and tendon tears, including intrasubstance tears, longitudinal splits, partial and complete rupture, inflammatory conditions and tendon tumors, as well as postoperative findings. In nerve imaging, US can support clinical and electrophysiological testing for detection of compressing lesions caused by nerve entrapment in a variety of osteofibrous tunnels of the limbs and extremities. Congenital anomalies, nerve tears, and neurogenic tumors can also be diagnosed. Overall, US is an effective technique for imaging tendons and nerves. In most cases, a focused US examination can be performed more rapidly and efficiently than MR imaging.

Sonography can demonstrate the normal internal anatomy of the rectus femoris and post-traumatic changes at the myotendinous junction of the central aponeurosis. Sonographic data correlate well with MR findings, and the low cost and wide availability of sonography make it the first-line technique in the evaluation of injuries of the rectus femoris.

We present the case of a 40-year-old man with rheumatoid arthritis who had a painless left inguinal mass. Sonographic examination revealed a large soft tissue mass with mixed internal echotexture and regular borders extending inside the pelvis and into the proximal portion of the thigh. Sonography also showed communication between the bursa of the iliopsoas muscle and the hip cavity, with intra-articular synovitis and erosion of the ileum. Giant iliopsoas bursitis secondary to hip involvement in rheumatoid arthritis was diagnosed on the basis of the sonographic findings. This diagnosis was confirmed by MRI.

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