The Anterior Cruciate Ligament (ACL) is the most common ligament injured in the knee, causing approximately 150,000 surgeries in the U.S. and costing $2.5B annually. ACL injury results in pain and instability of the knee and requires athletes to completely stop playing their sport. Currently, ACL injury is assessed clinically through the pivot shift test, which is a test capable of predicting knee function after an ACL injury. However, given the subjective nature of the test, criticism over validity arises from the variations in interpretation and performance and this leads to instability in 10-30% of patients post-operatively. The PIVOT application will reside on an iPad, and will track and analyze knee motion (via 3 circular markers placed on pre-determined bony prominences) to output quantitative information regarding translation of the knee. Using the objective output from the PIVOT application, physicians can obtain a better assessment of the necessary degree of surgery. The Coulter funding will facilitate upgrades to software, and allow an addition of 5-10 centers to the existing multi-center trial, to further validate PIVOT adoption and possibility of standardization throughout the field of Orthopedics.