infraclavicular fossa infraclavicular fossa the infraclavicular fossa is an indentation, or fossa, immediately below the clavicle, above the third rib and between the deltoid muscle laterally and medioclavicular line medially. infraclavicular fossa (mohrenheim's fossa)anterolateral view of head and neck (infraclavicular fossa labeled at bottom right)detailsidentifierslatinfossa infraclavicularista98a01.2.03.003ta2248fma61541anatomical terminology