Elbow instability in athletes comprises a wide spectrum of pathology, ranging from medial instability in the throwing athlete to traumatic posterolateral rotatory instability. The aim of this chapter is to provide an overview of the common types of instability of the elbow and implications for management in the athlete. This chapter reviews relevant anatomical and biomechanical factors and their alterations in the unstable elbow. Clinical history, physical examination, and imaging studies necessary to diagnose these injury patterns will be presented. Finally, the treatment of medial and lateral elbow injuries and posterolateral rotatory instability of the elbow is discussed.