The 'quadriceps angle': correlation between clinical and radiographic measurements from a study in North Bengal

Introduction: Quadriceps angle (Q angle) is one of the most important indicators of stability of patello-femoral joint. Orthopedic surgeons often measure the Q angle clinically in patients suffering from patello-femoral joint dysfunction or in subjects particularly young active sportspersons who are prone to injury of this joint. But the clinical method of measurement of Q angle is not standardized, and its value depends on various methods used. But the radiological method of measurement of Q angle is more accurate. However, due to the expense and time involved, the clinical method is preferred over the radiological one in practice. Aim: This study was aimed at studying the correlation and regression between the radiographic Q-angle values and the clinical ones, so that the former can be predicted easily from the latter. Materials and methods: Q angle was measured both clinically and radiographically in both knee joints of 93 adult subjects in North Bengal Medical College and Hospital. Result: Statistically significant correlation followed by the regression analysis could reveal simple linear regression equations for predicting the radiological Q-angle values from the clinical Q angle, derived separately in both males and females in right and left sides, separately. Conclusion: Thus, from a known clinical Q-angle value, we can derive the respective radiological Q angle, indirectly avoiding the entire troublesome maneuver in regular practice. So the present study recommends this method in clinical fields because this is a more rational and ideal approach to estimate the radiological Q angle. Increase in the Q angle beyond 20-22° predisposes to patellar dislocation which should be kept in mind while screening athletes, especially females. This tendency can be countered by quadriceps exercises and appropriate footwear.