Objective: The purpose of this study is to decrease the amount of error when measuring Q–angles using a goniometer by the new method, a private system developed at the I.R's university of social welfare & rehabilitation sciences (USWR) by Investigator.

Materials & Methods: Fourty subjects with Eighty healthy knees participated in this methodologic study. One investigator participated in data collection who is a licensed physical therapist and has over 6 years of clinical experience in orthopedic physical therapy. He has designed and experienced with new method and computer program. Quadriceps angles measured bilaterally for 40 subjects were recorded. Reliability and validity with new method of the measurements were calculated with Intraclass Correlation Coefficient (ICC) & Repeated Measurement for new method and compared it's result with goniometry in contrast with radiography.

Results: The ICC for measuring Q-angle with a new method versus the radiography was 0.935, while the ICC for measuring Q-angle with the goniometry versus the radiography was 0.696. The ICC between measures three times obtained with a New Method was 0.974.

Conclusion: There is a high association between measures of Q-angle obtained with a new method compared to those obtained with radiography while this association for goniometry is low. Intratester reliability for new method is good and this method can applied as a good measurement method of Q angle.