knees knocking (together)
From Longman Dictionary of Contemporary Englishknees knocking (together)knees knocking (together)FRIGHTENEDCOLDif your knees are knocking, you are feeling very afraid or very cold → kneeExamples from the Corpusknees knocking (together)• Years later, Ogwen apprenticeship having been served, we began to aspire to their routes, knees knocking at our effrontery.