Not a knee-jerk reaction
Anterior cruciate ligament (ACL) tears present as acute injuries. This may be with contact or non-contact sport. In the case of a non-contact injury, the history is usually of a patient playing sport with the foot planted attempting a side-stepping manoeuvre. The knee gives way with a popping sound and the patient falls to the ground.
Occasionally the patient may describe a hyperextension injury or a quadriceps active mechanism when the pop occurs as they jump into the air. The knee usually swells over several hours and it becomes