A detailed understanding of the anatomy and biomechanics of the lateral knee is essential for the clinical diagnosis and surgical treatment of lateral-sided knee injuries. In the past, the structure and function of the lateral and posterolateral knee was poorly understood and was dubbed by some as "the dark side of the knee." However, recent advances in quantitative anatomy and biomechanics of this region have led to the development of anatomic-based reconstruction techniques and improved objective and subjective patient-based outcomes. Although the lateral knee consists of 28 unique structures, the primary lateral knee stabilizers include the fibular collateral ligament, popliteus tendon, and popliteofibular ligament. Together, these structures function to resist lateral compartment varus gapping and rotatory knee instability. This work will summarize the current state of knowledge regarding the anatomy and biomechanics of the lateral knee structures, while emphasizing implications for surgical treatment.