6.2 Signals of the Muscles and Motions

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biking. In the worst case the patients lose their earning capacity and their independ-

ence.

However, the human joint angles deliver crucial information of the pathological

mobility of the body. In this regard the ground reaction force of the feet is an import-

ant variable for the discussion about the load on the human body and the properties

of the balance between the sides of the body. For the documentation of the patholo-

gical behaviour of the body, a acoustic-kinetic analysis system developed for the use in

gonarthrosis [36] is used. The system consists of three measurement systems to detect:

1.

the acoustic emission of the knee,

2.

the ground reaction force of the feet and

3.

the joint angles of hip, knee and ankle.

The three independent systems were not technical coupled and on account of this

the recordings of the data were carried out in an asynchronous manner with different

sampling rates. For an effective assessment the three data sets had to be synchronised.

In the following discussion the approach is shown using the example of force and

joint angle signals. This would be a special challenge because two different physical

measured variables had to be coupled. Attributes of the signals had to be worked out

to achieve the synchronisation of the measured data. The process will be exemplified

by means of a clinical case.

Clinical Case

The patient of the presented clinical case is a female, 68 years old and has a body mass

of 60 kg. The height of the patient is 163 cm. The patient suffers from pain in the left

knee joint that occurs occasionally during routine movements and frequently under

physical strain, during sports and gymnastics. Arthrosis of the left knee joint was sus-

pected in previous investigations. In the rehabilitation clinic the physiotherapist has

examined the patient to develop the therapy. To have some more objective informa-

tion for the development of the therapy the acoustic-kinetic joint analysis system was

applied during the examination of the patient (cf. Figure 6.8). During the examination

the patient has to execute the standard movement of the acoustic-kinetic joint ana-

lysis. The standard movement are three knee bends executed one after another in the

timespan of 10 seconds [78]. Prior to this the patient was invited to execute the three

knee bends in her own manner [35].

To document the motion and the effect of balance of the patient the ground reac-

tion force under the feet and the joint angles of the lower extremities were measured.

The third measurement of the acoustic emission of the knee joint will not be the issue

in this discussion. For further information see [37], [36] and [35].