Understanding of the etiology and pathology of hip instability has increased in recent years as new information has emerged regarding the disease processes of the hip. Hip instability, heretofore considered uncommon in clinical practice, is increasingly recognized as a pathologic entity. Instability may be classified as traumatic or atraumatic, and diagnosis is made based on patient history, physical examination, and imaging studies. Plain radiography, MRI, MRI arthrography, and hip instability tests (eg, posterior impingement, dial) can be used to confirm the presence of instability. Nonsurgical management options include physical therapy and protected weight bearing. Surgical intervention, whether arthroscopic or open, is required for large acetabular fractures and refractory instability. Knowledge of the etiology and evolving research of hip instability is essential to understand the spectrum of hip disease.