[Acromioclavicular joint : The "forgotten" joint]

Besides osteoarthritic changes, traumatic and posttraumatic lesions are the most frequent alterations of the acromioclavicular (AC) joint. The Rockwood classification is used to describe posttraumatic lesions. The most important screening modality is anteroposterior x‑ray imaging, preferably with weight bearing and side to side comparison. Magnetic resonance imaging (MRI) without weight bearing is superior to x‑rays in analyzing and classifying AC joint dislocations. Postoperative imaging and assessment of arthritic alterations are usually carried out using x‑ray images and MRI is used as an additional examination modality. Sonography is only of limited value. Multidetector computed tomography (MDCT) is usually not used as a primary imaging modality for the AC joint; however, it can be analyzed simultaneously whenever the shoulder joint is being investigated with MDCT.