What are the three components of the "unhappy triad" injury in the knee?

The "unhappy triad" refers to a common knee injury that typically occurs during sports activities, especially contact sports where a force is applied to the knee while the foot is planted. The components of this injury are a combination of ligaments and meniscal structures that are often affected simultaneously due to the nature of the trauma.

Injuries to the anterior cruciate ligament (ACL), the medial meniscus, and the tibial collateral ligament (also known as the medial collateral ligament, or MCL) often occur together when there is a stress applied to the knee, usually from an external force or sudden directional change. The ACL is critical for stabilizing the knee during dynamic movements, while the MCL provides support on the inner side of the knee, and the medial meniscus acts as a shock absorber and stabilizer for the joint.

Understanding these components is crucial since injuries to these structures can severely impact knee function, and they often require a well-structured rehabilitation program or surgery for recovery. Effective treatment relies on a clear understanding of which specific structures are involved in the injury.