Where does the costoclavicular ligament attach?

The costoclavicular ligament attaches between the clavicle and the first rib, providing stability to the sternoclavicular joint. This ligament plays a crucial role in maintaining the position of the clavicle relative to the thoracic cage, especially during arm movement and activities that involve the upper extremities. By connecting the first rib to the inferior surface of the clavicle, it helps to limit excessive movement of the clavicle and assist in protecting underlying structures, such as nerves and blood vessels, as they pass from the thorax to the arm.

The other options involve anatomical structures that do not relate to the costoclavicular ligament. For instance, the connection between the scapula and the humerus pertains to the shoulder joint's functional anatomy, which involves different ligaments like the glenohumeral ligaments. The sternum and clavicle connection refers specifically to the sternoclavicular joint but does not involve the costoclavicular ligament. Lastly, the ulna and radius are forearm bones that connect at the elbow and wrist but are not related to the ligaments associated with the clavicle and first rib.