Chronic myofascial pain of the cervical spine and shoulders is commonplace in clinical practice and is often related to adverse posture during work conditions in our lifestyle. The diagnosis is clinical and injections of the neck/shoulder muscles, especially the upper trapezius, are commonly performed in a blinded way. The anatomy of the posterior compartment of the neck is complicated, and several neurovascular structures are located nearby the trapezius and levator scapulae muscles in the inter-fascial planes. In this case of ours, we describe in details the sono-anatomy of the lower neck and propose a posterior ultrasound-guided real-time in-plane approach to inject the muscle belly of the upper trapezius, i.e. avoiding the superficial and deep branches of the transverse cervical artery and the spinal accessory nerve.