Which sign helps to detect the presence of a deep vein thrombosis?

The presence of a deep vein thrombosis (DVT) can be indicated by Homan's sign, which involves dorsiflexing the foot while the knee is extended. If this maneuver elicits pain in the calf, it may suggest the presence of a clot in the deep veins. Homan's sign is a clinical test commonly used by practitioners to evaluate potential DVTs, although it is worth noting that the reliability of this sign has been debated in modern medical literature.

Other signs mentioned in the options serve different purposes. The valgus test is used primarily to assess ligament integrity in the knee, specifically the medial collateral ligament. The Trendelenburg sign is utilized to evaluate hip stability and gluteal muscle function rather than venous status. The adductor test assesses adductor muscle strength or flexibility but is not related to detecting venous thrombosis. Thus, Homan's sign is the most relevant to diagnosing DVT among the choices presented.