What Are the Long-Term Implications of the Patient With Recurrent Instability in the Setting of Untreated ACL Injuries?

Some patients with anterior cruciate ligament (ACL) tears will not develop recurrent instability and can be treated conservatively. These patients have been termed copers. Unfortunately, there is no way to accurately predict which patients may fall into this small group. The majority of active patients with an untreated ACL tear will experience recurrent instability. Recurrent episodes of instability can lead to three detrimental changes in the knee: (1) meniscus injury, (2) articular cartilage injury, and (3) progressive knee instability. I will discuss each of these in turn.