Outcome instruments have become an essential part of the evaluation of functional recovery after anterior cruciate ligament (ACL) reconstruction. Although the clinical examination provides important objective information to assess graft integrity, stability, range of motion, and strength, these measurements do not take the patient's perception into account. There are many knee outcome instruments, and it is challenging for surgeons to understand how to interpret clinical research and utilize these measures in a practical way. The purpose of this review is to provide an overview of the most commonly used outcome measures in patients undergoing ACL reconstruction and to examine and compare the psychometric performance (validity, reliability, responsiveness) of these measurement tools.