Partial anterior cruciate ligament (ACL) tears are often difficult to diagnose and treat. Recent interest in the literature has focused on performing selective-bundle ACL reconstruction in patients with symptomatic partial ACL tears when one of the ACL bundles is intact. However, the clinical examination, magnetic resonance imaging, and arthroscopic evaluation of partial ACL tears may not correlate, and proper assessment of the integrity of the intact portion of the ACL continues to be a challenge. If a selective-bundle ACL reconstruction is performed in a patient with an apparently intact but structurally damaged individual bundle, the outcome would be compromised by leaving the damaged bundle in place. This technical note provides a description of a simple and reliable arthroscopic method to aid in the diagnosis of a partial ACL tear. The use of this method to assess remaining ligamentous tissue will assist surgeons in deciding for or against selective-bundle ACL reconstruction.