The angle formed between the longitudinal axis of the femur, representing the pull of the quadriceps muscle, and a line that represents the pull of the patellar tendon. A clinical measure of the angle is obtained by connecting the central point of the patella with a line through the anterior iliac spine above and with a line through the tibial tuberosity below. The Q-angle is normally less than 15° in men and 20° in women when the quadriceps are relaxed. The angle becomes smaller when the quadriceps are contracted. A Q-angle greater than 20° increases the likelihood of the quadriceps pulling the kneecap laterally, increasing the risk of knee disorders such as patellofemoral pain syndrome.
Subjects: Sports and Exercise Medicine.