The Rotating Knee – Preventing it From Spinning Out

The knee joint is a complex and pivotal structure in the human body, providing mobility and support for various daily activities. One of the key components responsible for maintaining stability in the knee is the Anterior Cruciate Ligament (ACL). Comprising two distinct bundles – the anteromedial and posterolateral bundles – the ACL acts as a critical stabilizer for the knee.

The anterolateral bundle mainly functions to stabalise the knee from forward motion of the leg. On the other hand, the posteromedial bundle of the ACL, situated on the inner side of the knee joint, plays a crucial role in controlling internal rotation of the tibia, a movement that is frequently associated with various athletic activities.

The posteromedial bundle works in tandem with the other components of the ACL to stabilize the knee joint, especially in situations where rotational forces are applied. This is particularly important in sports that involve quick changes in direction, as well as in everyday activities that require agility.

Another important structure of the knee that plays a role in maintaining rotational stability is the posterolateral complex. It is a network of structures on the outer and back aspects of the knee, including the lateral collateral ligament (LCL), popliteus tendon, and popliteofibular ligament. These components work in harmony to stabilize the knee during rotational movements, such as pivoting, cutting, and changing direction.

The primary function of the PLC is to resist excessive external rotation and varus stress applied to the knee. During activities like running, jumping, or participating in sports, the knee is subjected to various forces that can potentially lead to rotational instability. The PLC acts as a critical checkpoint, preventing the knee from undergoing excessive rotation and maintaining stability during these dynamic movements.

Recent attention has turned to the anterolateral ligament (ALL) for its crucial role in controlling rotational stability. This relatively understudied ligament is gaining prominence for its impact on knee function and injury prevention. The anterolateral ligament is a thin, band-like structure located on the outer aspect of the knee joint. It originates near the lateral femoral epicondyle and extends diagonally across the knee to attach to the anterolateral tibia. Although the existence and function of the ALL were debated for many years, advanced imaging techniques and anatomical studies have now solidified its place in our understanding of knee biomechanics.

The primary function of the anterolateral ligament is to counteract excessive internal rotation and varus stress applied to the knee during various activities. This is particularly crucial in dynamic movements such as cutting, pivoting, and decelerating. The ALL acts as a key player in preventing the tibia from excessively rotating and contributing to the overall stability of the knee joint.

Lastly, the menisci, located between the femur and tibia, serve to distribute load, absorb shock, and stabilize the knee during movement. Ramp lesions and root tears, however, represent disruptions in the integrity of the meniscus.

• Ramp Lesions: Ramp lesions typically occur in the posterior horn of the medial meniscus, where the meniscus attaches to the tibia. These injuries involve a detachment of the meniscus from the tibial plateau, creating a ramp-like structure. The significance of ramp lesions lies in their potential to cause rotational instability by altering the distribution of forces within the knee.

• Root Tears: The meniscal root is the attachment point of the meniscus to the tibia. Tears at this crucial juncture, known as root tears, can compromise the meniscus's ability to resist rotational forces. When the root is damaged, the entire meniscus may become less effective in stabilizing the knee, leading to an increased risk of rotational instability.

Relevance in Sports:

Athletes involved in sports that require sudden changes in direction, quick pivots, and rotational movements heavily depend on the knee structures to work in harmony for optimal knee stability. Sports like martial arts, rugby, basketball, and football, where players frequently engage in rapid direction changes, highlight the critical role of these structures in preventing injuries and ensuring peak performance.