Long head biceps (LHB) tendon pathologies are becoming increasingly recognized causes of shoulder pain in the published literature. Instability of LHB presenting as dislocation or subluxation has been recently recognized as a possible cause of disabling pain or discomfort of the shoulder. A clinical diagnosis of LHB instability is very difficult and often confounding because of association with other shoulder pathologies. However, an early diagnosis of LHB instability is important in order to prevent the evolution of lesions of the biceps pulley until an internal anterosuperior impingement of the shoulder (ASI) and subscapular tear occur. The advent of arthroscopy contributed to enhance understandings. The goal of this article is to describe an arthroscopic sign, the chondral print on the humeral head, associated with a LHB instability, that when present can be very useful to help the surgeon to make the diagnosis of unstable LHB tendon.