The first question is does navicular drop even need fixing? The really is no such thing as a “fix” for navicular drop as its a normal movement.
The navicular drop is how much that the height of the navicular drops between semi-weight bearing and full weightbearing or between the subtalar joint being in its neutral and relaxed positions (different people and different research studies use different definitions as to what it actually is). A person with a bigger foot will have more than a person with a smaller foot, so trying to define what is a normal amount of navicular drop (regardless of which definition you use) is always going to be a problem as it is dependant on foot size.
Navicular drop is a measure of ‘arch collapse’ or height of the navicular from the ground between two different conditions. It measures the sagittal plane positions of the height of the navicular (which is one of the components of what could considered to be involved in ‘overpronation‘ of the foot). It is also an observation made in determining the Foot Posture Index of the foot. Navicular drop does not measure the transverse movement of the midfoot that is also a component of ‘overpronation’ (navicular drift does that).
There is a lot of normal variability in navicular drop between people and those with a lot of it do not automatically mean that it needs a “fix”.
If the navicular drop is excessive and it is causing problems, you fix it by propping up the arch of the foot in the sagittal plane or use something like the short foot exercise to strengthen the arch muscles as a long term measure. However, that is not going to address issues with navicular drift in the transverse plane. It is complex and each case is going to need to be assessed and addressed as to what is the best way to fix the navicular drop, if it needs fixing.
