The foot is a crucial and complex piece of anatomy. It's made up of many different active and passive structures that play a role in synchronously absorbing ground reactive forces (GRF), and propulsion of the body.
Control & Stability
There is a complex, orchestrated interaction between active and passive structures which are overseen and controlled by the nervous system. You've got passive ligamentous structures meant to resist motion, which are also supported through the muscles of the foot, and active tissue which are the muscles creating and absorbing motion. The muscles of the foot further break into two categories. Intrinsic and extrinsic. The former are muscles that begin and end within the foot. The latter (extrinsic) are muscles that still directly insert into the bones and ligaments of the foot, but reach further up the leg proximally.
The windlass mechanism is a mechanical model that describes the manner which plantar fascia supports the foot during weight-bearing activities and provides information regarding the bio-mechanical stresses placed on the fascia. As you raise the great toe a shortening occurs of the plantar aponeurosis, and tight packs the bones of the foot. This creates a rigid lever for propulsion. Lowering of the great toe relaxes tension making the foot a supple adapter. It's an ingenious mechanism to shift from push-off, to landing.
Obviously dysfunction of the windlass mechanism may cause issues. For example, examining the windlass mechanism is important in the decision-making process in evaluating and treating plantar fasciitis.
Stiff shoes can inhibit the windlass mechanism. Going barefoot or minimalist shoes can be tremendously helpful in allowing the windlass mechanism to operate properly.
In treating plantar fasciitis, orthotics can be a temporary measure to reduce symptoms, but should be removed as soon as possible because they impair the windlass mechanism. This can unfortunately manifest other pathologies.
Full Body Troubles
With impairment of the mechanism that absorbs ground reactive forces the energy is not destroyed, it is rather transferred elsewhere. When measuring a top sprinter GRF of 5x their body-weight could be measured. For a marathon runner, impact duration increased significantly and GRF was 3x body-weight. This is to give you some perspective. With an impaired foot GRF of 3-5x your body-weight could in theory travel towards the knee, hip, and back. This is why we emphasize proper mobility and stability of the ankle and foot respectively. Massage & Bodywork
Massage therapy can be helpful to feed the nervous system new, novel information as we work the intrinsic and extrinsic muscles of the foot, as well as more passive structures. This can reduce pain symptoms greatly. Increasing mobility of the ankle and assessing / modulating the big toe & windlass mechanism can also set the foot up for future success.
As stated earlier it is important not to be too reliant on orthotics, but that extends to passive therapies as well. The most important element is empowering people to strengthen, stabilize, and rehab on their own. The first step is taking ownership of one’s own pain condition.