Background The mechanisms of anterior cruciate ligament injury in basketball are not well defined. Purpose To describe the mechanisms of anterior cruciate ligament injury in basketball based on videos of injury situations. Study Design Case series; Level of evidence, 4. Methods Six international experts performed visual inspection analyses of 39 videos (17 male and 22 female players) of anterior cruciate ligament injury situations from high school, college, and professional basketball games. Two predefined time points were analyzed: initial ground contact and 50 milliseconds later. The analysts were asked to assess the playing situation, player behavior, and joint kinematics. Results There was contact at the assumed time of injury in 11 of the 39 cases (5 male and 6 female players). Four of these cases were direct blows to the knee, all in men. Eleven of the 22 female cases were collisions, or the player was pushed by an opponent before the time of injury. The estimated time of injury, based on the group median, ranged from 17 to 50 milliseconds after initial ground contact. The mean knee flexion angle was higher in female than in male players, both at initial contact (15° vs 9°, P = .034) and at 50 milliseconds later (27° vs 19°, P = .042). Valgus knee collapse occurred more frequently in female players than in male players (relative risk, 5.3; P = .002). Conclusion Female players landed with significantly more knee and hip flexion and had a 5.3 times higher relative risk of sustaining a valgus collapse than did male players. Movement patterns were frequently perturbed by opponents. Clinical Relevance Preventive programs to enhance knee control should focus on avoiding valgus motion and include distractions resembling those seen in match situations.