What is a mechanism of an anterior cruciate ligament (ACL) sprain?

An anterior cruciate ligament (ACL) sprain often occurs through specific movements that place significant stress on the knee joint. The mechanism of an ACL injury typically involves knee hyperextension combined with rotation. This scenario frequently happens in sports that require sudden changes in direction, jumping, or landing, where the knee is forced into an extended position while the body is turning or twisting.

When the knee is hyperextended, the ACL is put under excessive strain, which can lead to a tear or sprain. In addition, the rotational movement at the hip and knee during these activities can further exacerbate the tension on the ligament, increasing the likelihood of injury. This mechanism is particularly common in sports such as basketball, soccer, and skiing, where pivoting and quick lateral movements are prevalent.

The other options describe less common mechanisms or scenarios that may not directly result in an ACL sprain. For instance, falling onto a flexed knee may stress different structures around the knee but is less likely to specifically cause an ACL injury. Similarly, impact to the medial side of the knee might affect the medial collateral ligament (MCL) rather than the ACL. Lastly, a degenerative disorder refers to gradual wear and tear over time, which isn't a specific acute mechanism of