 Multiple studies suggest that reduced postural orientation is a possible risk factor for both patello-femoral joint pain (PFP) and rupture of the anterior cruciate ligament (ACL). In order to prevent PFP and ACL injuries in adolescent athletes, it is necessary to develop simple and predictive screening tests to identify those at high risk. Single Leg Mini Squat (SLMS) is a functional and dynamic real-time screening test, which has shown good validity and reproducibility in evaluation of postural orientation of the knee in an adult population. The aim of this study was to determine the inter-tester reproducibility of SLMS in the age group of 9–10 and 12–14 years by evaluating postural orientation of the ankle, knee, hip and trunk. Further on, this study exemplify the divergence of kappa values when using different methods of calculating kappa for the same dataset.