**4.7 Comparative sound transmission test with tuning fork and stethoscope**

The patient is placed supine with the lower extremities in extension and adduction; a 256-cycle/second tuning fork is placed on one knee and the sound is captured through a stethoscope, placing the diaphragm on the symphysis pubis; the tuning fork is placed on the opposite knee and the sound is compared to the first side (**Figure 4a** and **b**) [34–37]. If the sound is less on either side, it is considered positive for that side. If the DDC is bilateral, the perception of sound will be the same on both sides.
