Costoclavicular ligament

The costoclavicular ligament, also known as the rhomboid ligament, is a key stabilizing structure located just lateral to the sternoclavicular joint. Superiorly, it connects to the costal tuberosity on the undersurface of the medial end of the clavicle. Inferiorly, it descends in a lateral to medial direction to attach to the first costal cartilage and, in most cases, the medial end of the first rib.

By uniting the clavicle to the first rib and its costal cartilage, the costoclavicular ligament prevents excessive movement of the medial clavicle, stabilizing the sternoclavicular joint during various upper limb motions. It is closely associated with the subclavius muscle and its tendon, which typically inserts anterior to the ligament, while posteriorly it is related to the subclavian vein.