[Acoustical analysis of joint-sound through passive motion--with special reference to degenerative osteoarthrosis of the knee joints].

Sounds from the joints are still in the mysterious zone. It seems to be important to study the sound which occurs on motions. Here, a new analysing method and its clinical application are presented and discussed. The joint which is studied, is moved in some ranges for four seconds in the unechoic chamber, and a special microphone is kept to touch on the pan-articular skin manually throughout the motion. These collected sounds are analyzed with a narrow band spectrum analyzer (Br uel & Kjaer Co., 2031 Type) and a computer. In the unechoic chamber, it may diminished the background noises. The narrow band spectrum analyzer made it possible not to use the magnetic tape which usually induced much noise. Furthermore, as the computer system is utilized, it become easy to compile the data of each frequency analysis and to obtain over all value, with which the sound volume can be compared with each other. The over all value means an integrated volume of each joint sound. In this paper, joint sound were obtained from normal and pathological human joints. In the normal cases, the frequency analysis data showed almost flat spectrum curves, and the total over all values (0.5 kHz to 5 kHz) were usually less than 80 dB. On the other hand, in the pathological joints which had bony changes affected by rheumatoid arthritis, degenerative osteoarthritis, fracture, and others, the frequency analysis showed elevated curves in range from 0.5 kHz to 4.0 kHz, and the total over all value increased in each pathological joint. In 85 cases of osteoarthrosis of the knee joints, the total over all values were a wide dispersion from 76 to 104 dB. And these values and radiological grading (by Swanson) correlated to each other. The over all values at each 0.5 kHz interval, especially from 0.5 to 1.5 kHz, were maximum ones in each radiological gradings. It is concluded that these results in osteoarthrosis cases, are related to with radiological gradings.