PURPOSE/HYPOTHESIS: The purpose of this observational study was to determine which factors, including sex, are associated with increased rotatory knee laxity in collegiate athletes with no history of knee injuries. It was hypothesized that increased rotatory knee laxity, measured by a quantitative pivot shift test, would correlate with female sex, increased anterior translation during the Lachman test, generalized ligamentous laxity, and knee hyperextension. METHODS: Ninety-eight collegiate athletes with a median age of 20 (range 18-25) years with no history of knee injuries were tested. IKDC and Marx activity scores were obtained and subjects underwent measurement of anterior translation during the Lachman test with a Rolimeter and measurement of knee hyperextension with a goniometer for both knees. A standardized pivot shift test was performed in both knees and quantified using image analysis technology. Generalized ligamentous laxity was assessed using the modified Beighton score. RESULTS: The average anterior translation of the lateral compartment during the pivot shift test was 1.6 mm (range 0.1-7.1) with a mean side-to-side difference of 0.6 mm (range 0-2.7). The average anterior translation during the Lachman test was 9.0 (range 2-15). The anterior translation of the lateral compartment during the pivot shift test was significantly higher in females (median, 1.6; range 0.3-4.9) than in males (1.1, 0.1-7.1 mm) (p < 0.05). Anterior translation of the lateral compartment during the pivot shift test was significantly correlated with anterior translation during the Lachman test (r = 0.34; p < 0.05). There was no significant correlation between anterior translation of the lateral compartment during the pivot shift test and knee hyperextension or modified Beighton score (n.s). CONCLUSION: The data from this study show that female sex is associated with increased rotatory knee laxity measured during the pivot shift test and anterior translation during the Lachman test in collegiate athletes. In the future, these data may be helpful in diagnosing and managing ACL injuries in athletes and could be used in the clinic as a baseline by which to compare and identify patients who might exhibit increased rotatory laxity. LEVEL OF EVIDENCE: Diagnostic level II.