Don O’Donoghue (1950) described a particular acute injury of the knee in athletes (“also of high school age”) that he described as “an unhappy triad”. It consisted of: 1) rupture of the Medial Collateral Ligament (MCL), 2) damage to the Medial Meniscus (MM) and 3) rupture of the Anterior Cruciate Ligament (ACL)

We have reviewed the arthroscopic findings of 34 consecutive knees (ages 12 to 16 years) with complete rupture of the ACL. In 21 cases the injury was acute, and the remaining were chronic of had had more than one traumatic episode at the time of arthroscopy.

Out of the 34 cases, 26 had associated meniscal injuries: 4 MM; 14 Lateral Meniscus (LM) and 8 MM plus LM. Acute ACL injuries were associated mainly with LM damage (MM/LM: 1/5) whereas, in the chronic injuries, there were no such differences (MM/LM: 1/1). Out of the 21 acute LCA injuries there were 17 cases of acute rupture of the MCL.

Conclusions: 1- Contrary to what has been widely accepted, also in pre-adolescent and adolescent, Acute ACL ruptures are more frequently associated with LM damage that with MM tears. 2- Most injuries of the MM associated to ACL injuries (particularly “bucket handle” tears) are the result of a previously ACL unstable knee.