Final answer:
The anterior cruciate ligament (ACL) is the ligament that becomes tight during knee extension, preventing hyperextension and providing stability to the knee joint.
Step-by-step explanation:
The bundle of the anterior cruciate ligament (ACL) that becomes tight during knee extension is significant for maintaining knee stability. Within the knee joint, there are several crucial ligaments that contribute to its stability. The ACL, along with the posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), plays a vital role in knee joint function. The ACL is one of the two intracapsular ligaments, extending from the anterior, superior surface of the tibia to the inner aspect of the lateral condyle of the femur. It primarily acts to resist hyperextension of the knee when the knee is extended. This ligament ensures that the knee does not bend backward during movement. On the other hand, the PCL supports the knee when it is flexed and bears weight, such as when walking downhill, by preventing the femur from sliding off the top of the tibia.
The ligament that is tight in knee extension is the anterior cruciate ligament (ACL). The ACL is an intracapsular ligament of the knee that extends from the anterior, superior surface of the tibia to the inner aspect of the lateral condyle of the femur. It resists hyperextension of the knee when it is fully extended.