Joint-sounds in gonoarthrosis--clinical application of phonoarthrography for the knees.

Auscultation is one of the oldest methods of diagnosis. It has been extensively used in examining various organs of the body, but its use for studying joint-sounds is still an unexplored area of research. In our clinic, a new analyzing system has been developed and its clinical application has been practiced since 1980. The joint-sounds are analyzed with a narrow band spectrum analyzer and a computer. The spectrum of background noise is then subtracted from the linear averaged spectrum to obtain the phonoarthrograph. Our study showed that all the joint-sounds exist at a point lower than 3.5 kHz with the majority of them being lower than 2.5 kHz. Therefore, we believe that there are mainly two kinds of joint-sounds, that is, at the low frequency sound level (L type) and at the high frequency sound level (H type). The significance of joint-sounds at the high frequency sound level is unknown but we suggest that it is due to the thickness and the hardness of the articular surface. Next the significance of joint-sounds at the low frequency sound level were investigated. We think that joint-sounds reflect not only on the change of bone but also on something else due to osteoarthrosis. The sounds which are concerned with the changes as seen on the X-ray films exist at the low frequency sound level mainly from 0.5 kHz to 1.0 kHz. We believe that this method is noninvasive and useful for the diagnosis of osteoarthrosis of joints.