Which ligaments and structures are affected in the unhappy triad?

The unhappy triad is a well-known injury pattern typically sustained during athletic activities, particularly in sports involving sudden changes in direction, such as football or soccer. This injury involves three key structures in the knee: the anterior cruciate ligament (ACL), the medial collateral ligament (MCL), and the medial meniscus.

When a force is applied to the lateral side of the knee while the foot is fixed on the ground (which is common during certain types of tackles or falls), it can cause a valgus stress on the knee. This stress can result in damage not only to the ACL and MCL, both of which are crucial for knee stability, but also to the medial meniscus due to the nature of the injury mechanics. The medial meniscus can become torn as it is compressed between the femur and tibia during the forceful movement.

The combination of these three injuries is significant because they often occur together due to their anatomical and mechanical relationships. Recognizing this triad assists in both diagnosis and treatment plans in sports medicine, emphasizing the need for careful rehabilitation to restore function and prevent future injuries.