Introduction: Diseases of the musculoskeletal system are often accompanied by postural deformity or malalignment. Genu varo or genu valgo can be found in the knees. It is necessary to have a diagnostic support test for diagnosis as well as for follow-up of cases since these diseases are frequently progressive and over time have serious repercussions on patient quality of life. Objective. To evaluate a software program that processes digitalized photographs as a diagnostic test for measuring the mechanical axis in patients with genu varo and genu valgo.
Materials and methods: The mechanical axis in both knees was measured by means of radiography (golden standard) and by means of a software program (proposed diagnostic test) in one hundred patients. Mechanical axis was considered to be abnormal when the angle was equal to or greater than four degrees. Sensitivity, specificity, positive predictive value, and negative predictive value were determined. Interobserver variation was evaluated with kappa statistics.
Results: In relation to right knee genu varo, sensitivity, specificity, positive predictive value, and negative predictivie value were 0.84, 0.87, 0.84, and 0.87, respectively, and for the left knee values were 0.86, 0.87, 0.84, and 0.89, respectively. For genu valgo in the right knee, sensitivity, specificity, positive predictive value, and negative predictive value were 0.78, 0.98, 0.95, and 0.92, respectively, and in the left knee were 0.88, 0.95, 0.88, and 0.95, respectively. Kappa value was 0.9 in the right knee and 0.8 in the left knee.
Conclusion: The software program (diagnostic test) was useful for diagnosing genu varo or genu valgo, representing a safe and low-cost study.