Background:

Smartphones have become a fundamental part of our society, not only everyday, but also professional, since many applications have emerged for the health field. The objective of the study was to analyze the reliability and concurrent validity of an app for iPhone in relation to traditional measurement.

Material and methods:

A non-experimental, double-blind validation and descriptive study. On a sample of 21 subjects, four measurements of knee mobility were performed. Two using universal goniometer (GU) and two through the application Goniometer-Pro (G-Pro) for IPhone. The X-ray was used as a reference measure of the knee flexion angle and was analyzed by a single evaluator who compared this result with that of the other evaluators.

Results:

The difference between the average intra-group values was 3.148o (± 2.669o) for GU and 2.476o (± 2.638o) for G-Pro. The inter-group mean difference reached 5.45o. The Inter-observer reliability was 0.990 for GU and 0.993 for G-Pro; as for validity, the values obtained were 0.976 for GU and 0.992 for G-Pro.

Conclusions:

The G-Pro app is a reliable tool with a high accuracy to measure the knee flexion angle. Its results are slightly superior and more accurate to those of traditional instruments.