The high rate of ACL injury has led to the need for large-scale injury risk screening to aid in prevention. Cost and time alternatives to three-dimensional assessments of knee injury risk factors are necessary for largescale, clinical use. The purpose of this study was to determine the expert versus novice interrater reliability and test-retest reliability of the frontal plane projection angle (FPPA) during the single-leg squat (SLS) test. Excellent interrater reliability was demonstrated for session 1 and session 2. Excellent intrarater (i.e., test-retest) reliability was demonstrated for both the novice and expert. The minimal training requirements and excellent reliability of the FPPA during the SLS test make it a key screening tool for large-scale assessment of injury risk.