In an ACL tear, which other injuries are commonly found?

• A. PCL tear
• B. MCL / Medial meniscus tears
• C. Patella avulsion fracture
• D. Tibial plateau fracture

Answer: (B)

When the ACL tears, there’s often accompanying injury to the knee’s inner structures because the common mechanism involves valgus stress and rotational force on a planted foot. This pattern frequently damages the medial collateral ligament and the medial meniscus, which sit on the same medial side of the knee and are stressed together during the twisting and valgus moment. That combination—ACL tear with injury to the MCL and medial meniscus—fits the well-known pattern sometimes described as the unhappy triad.

Less commonly, the PCL is injured with different mechanisms (like a direct blow to the proximal tibia, often in dashboard injuries), and bone injuries such as tibial plateau fractures or a patellar avulsion fracture tend to occur with higher-energy forces or different loading patterns. So the most typical co-injury with an ACL tear is the medial collateral ligament and medial meniscal damage.