Elbow incongruity is an important factor regarding the treatment and prognosis of elbow dysplasia. Our purpose was to determine the sensitivity and specificity for radiographic detection of elbow incongruity in clinical patients, to establish inter- and intraobserver variation for different parameters, and to evaluate the possibility of radiographic grading of incongruity. Standard radiographic projections were acquired from 29 incongruent and nine congruent elbows of dogs of various ages and breeds. Computed tomography (CT) was used to diagnose and grade the incongruity. All radiographs were evaluated by four observers for detection and grading of elbow incongruity. Sensitivity, specificity, inter- and intraobserver variability were calculated. The mean sensitivity for detection of incongruity was very good (88.8%) with a mean specificity of 91.7%. Correct grading of incongruity was difficult. The radioulnar step and the widening of the humeroulnar and humeroradial joint space were seen most frequently. Intraobserver and interobserver variability were fair to excellent (Kappa = 0.372–0.809), depending on the investigated parameters. Radiography is valuable to screen for elbow incongruity. In over 91% of the patients, a clear distinction could be made between a congruent and an incongruent joint grading was not possible.