Alan C Merchant1, Ryan Fraiser2, Jason Dragoo3, Michael Fredericson4. 1. Stanford University Sports Medicine, 450 Broadway St., Redwood City, CA 94063, USA. Electronic address: kneemd@sbcglobal.net. 2. Stanford University Sports Medicine, 450 Broadway St., Redwood City, CA 94063, USA. Electronic address: ryanfraiser@gmail.com. 3. Stanford University Sports Medicine, 450 Broadway St., Redwood City, CA 94063, USA; University of Colorado Health, Steadman Hawkins Clinic, Denver, 175 Inverness Drive West Suite 200, Englewood, CO 80112, USA. Electronic address: j.dragoo@ucdenver.edu. 4. Stanford University Sports Medicine, 450 Broadway St., Redwood City, CA 94063, USA. Electronic address: mfred2@stanford.edu.
Abstract
BACKGROUND: Studies have shown that Q angle measurements were unreliable. Imaging studies have largely replaced the Q angle for measuring tibial tubercle lateralization. Creating a standardized protocol to measure the Q angle, with normative values, would provide a reliable reference without expensive imaging techniques. METHODS: Thirty men and 27 women without history of knee problems or family history of dislocating kneecaps were subjects. Exclusion criteria were: patellofemoral abnormalities upon examination. We measured the Q angles of both knees using a standardized protocol and a long-armed goniometer. These data were analyzed to calculate normative values. RESULTS: For all subjects, the mean was 14.8° (≈15°), 95% confidence interval (CI): ±5.4°. The male mean was 13.5°, 95% CI: ±5.2°. The female mean was 15.9°, 95% CI: ±4.8°. There was no significant difference between the right and left knees of the males (p = 0.52), nor of the females (p = 0.62), Beta = 0.14. The 2.4° difference between male and female means was due to the average height difference between the men and women. CONCLUSIONS: This study provides a standardized Q angle measurement protocol to assess tibial tubercle lateralization at a patient's first encounter (and intra-operatively) without resorting to expensive imaging studies. These values provide a reliable reference for clinical comparison, and will allow all clinicians and sports medicine personnel to assess tubercle lateralization with reliability and validity. When using this protocol, the term "Standard Q Angle" (SQA) should be used, to avoid confusion with other measurement protocols.
BACKGROUND: Studies have shown that Q angle measurements were unreliable. Imaging studies have largely replaced the Q angle for measuring tibial tubercle lateralization. Creating a standardized protocol to measure the Q angle, with normative values, would provide a reliable reference without expensive imaging techniques. METHODS: Thirty men and 27 women without history of knee problems or family history of dislocating kneecaps were subjects. Exclusion criteria were: patellofemoral abnormalities upon examination. We measured the Q angles of both knees using a standardized protocol and a long-armed goniometer. These data were analyzed to calculate normative values. RESULTS: For all subjects, the mean was 14.8° (≈15°), 95% confidence interval (CI): ±5.4°. The male mean was 13.5°, 95% CI: ±5.2°. The female mean was 15.9°, 95% CI: ±4.8°. There was no significant difference between the right and left knees of the males (p = 0.52), nor of the females (p = 0.62), Beta = 0.14. The 2.4° difference between male and female means was due to the average height difference between the men and women. CONCLUSIONS: This study provides a standardized Q angle measurement protocol to assess tibial tubercle lateralization at a patient's first encounter (and intra-operatively) without resorting to expensive imaging studies. These values provide a reliable reference for clinical comparison, and will allow all clinicians and sports medicine personnel to assess tubercle lateralization with reliability and validity. When using this protocol, the term "Standard Q Angle" (SQA) should be used, to avoid confusion with other measurement protocols.