Sensitivity versus specificity of phonoarthrography as an indicator for cartilage degeneration

In an attempt to update the idea of recording knee sounds, 400 osteoarthritic (OA) knees, 100 knees from a young age group (18-31 years) and 100 knees from an age-matching group (45-60 years) were recorded by a computerized device using a special program that enabled the conversion of sounds--recorded in a fixed lapse of time--to waves which were then analysed in terms of frequency/second and average amplitude. Radiological grading was done for all groups in order to compare both parameters. Reproducibility of the recordings for each knee was confirmed statistically. Phonoarthrography was found to be 100% sensitive for radiological changes and for clinically felt crepitus, simultaneously diagnosing early OA in 32.5% of subjects with no radiological changes and in 7.5% of subjects with no clinically felt crepitus. From the work it can be deduced that computerized phonoarthrography can diagnose early cases of OA and is excellent for assessing and following up cases. It may be regarded as an indicator for cartilage degeneration.