Far from being a uniplanar hinged joint, the knee experiences a complex mechanical environment in three translational planes and three rotational axes, constituting 6 degrees of freedom. The bony morphology and articular cartilage of the knee joint establish the foundational limits of joint motion, with further constraint and stability provided by passive and active stabilizers. The passive stabilizers include elements that are intra-articular – anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and menisci – or extra-articular – medial collateral ligament (MCL) and lateral collateral ligament (LCL). Dynamic stabilizers are principally antagonistic muscle groups including the anterior extensor mechanism and posterior hamstring musculature. Other elements that constitute the posterolateral corner (PLC), posteromedial corner (PMC), and anterolateral complex (ALC) are a combination of passive and active stabilizers which collectively provide a unique stabilizing function. In this review, the structure and function of the many elements comprising the knee joint are highlighted, imparting appreciation of the unique anatomy and biomechanics of the knee.