Nerve entrapment syndromes occur when peripheral nerves are compressed within anatomic tunnels or between structures. Carpal tunnel syndrome (median nerve at the wrist) is the most common. On ultrasound, an entrapped nerve typically shows focal swelling and increased cross-sectional area at and proximal to the compression site, with loss of the normal fascicular echotexture. Dynamic scanning can demonstrate the nerve catching or flattening with joint movement. Ultrasound-guided nerve hydrodissection and steroid injection are increasingly performed for treatment.