The angle formed by the bisection of two lines drawn from ASIS to the center of the patella and another line drawn from the center of the patella to the tibial tubercle. The angle is a measure of the tendency for the patella to move laterally when the quadriceps muscles are contracted (Dutton, Cooney). An increased Q-angle has been associated with an increased risk of patellar instability (Cooney). The normal Q-angle is 8°–17° in males and 12°–20° in females, with it being suggested that an increased Q-angle (greater than 20°) is associated with an increased risk of anterior knee pain and patellar instability (Cooney). Theoretically, a higher Q-angle increases the lateral pull of the quadriceps femoris muscle on the patella and potentiates patellofemoral disorders (Mohammed).
An increased Q angle is traditionally associated with valgus knees and some of the highest Q angles are found in patients with a combination of genu varus and proximal tibial torsion (Dutton). Research shows that Q-angle is not a reliable indicator of patellar instability, however it may be a contributor. There is a clear need to further develop methods to more fully characterise the knee and factors contributing to patellar instability (Atanda).
- Dutton M. Orthopaedic Examination, Evaluation, and Intervention. 2nd ed: The McGraw-Hill Companies, Inc.; 2008.
- Cooney, A., Kazi, K., Caplan, N., Newby, M., St. Clair, G., & Kader, D. (2012). The relationship between quadriceps angle and tibial tuberosity-trochlear groove distance in patients with patellar in patients with patellar instability.
- Mohammed, J., Mohammed, H., Abdinejad, F., & Hamid, N. (2007). Q-angle: An invaluable parameter for evaluation of anterior knee pain.Arch Iranian Med, 10(1), 24-2
- Atanda, Alfred, Suken Shah, and Kathleen O'Brien. "Osteochondrosis: Common Causes of Pain in Growing Bones." American Academy of Family Physicians 83.3 (2011):