Radiographic determination of the quadriceps angle in cats shows good to excellent repeatability but moderate reproducibility

Objective: To report the radiographic quadriceps angle (Q-angle) in a cat population and to determine the repeatability and reproducibility of the method of measurement. Methods: A population of client-owned cats presented to a single referral center from October 2024 through April 2025 was submitted to a radiographic study. Cats anesthetized for any procedure and free of orthopedic and neurologic conditions affecting the hind limbs were included. Orthopedic Foundation for Animals guidelines were used for positioning. Radiographs were reviewed, and the Q-angle was calculated. The repeatability and reproducibility of the method were subsequently determined. Results: 27 cats were included for radiographic study. The mean Q-angle was 15.7 ± 1.1° (95% CI, 12.6° to 18.7°). There was no significant correlation between the Q-angle value and the age, sex, or breed of cats. The intraclass correlation coefficient for interobserver agreement was 0.63. Intraclass correlation coefficients for intraobserver agreement were 0.90, 0.88, and 0.94. Conclusions: The mean radiographic Q-angle in this cat population was 15.7 ± 1.1° (95% CI, 12.6° to 18.7°). Inter- and intraobserver agreement evaluations were consistent, with moderate reproducibility and good to excellent repeatability of the method of measurement. Clinical Relevance: To our knowledge, this is the first study reporting the radiographic Q-angle in a population of cats. It can be used as a supplementary tool for anatomic evaluation. Further studies are needed to determine its usefulness, especially in the planning of corrective surgeries.