An orthotic is an externally applied device used to control a body part.
In the context of ankle osteoarthritis the options available are either braces or modifications of shoewear.
How do they work?
They work by reducing the forces going through the ankle and therefore reducing the symptoms from a failing joint.
The rocker sole
During walking, the ankle joint acts as a "rocker", allowing the body to progress forwards, over the foot which is initially "fully" in contact with the ground.
A rocker sole allows one to walk forwards normally with the shoe performing this function of the ankle. The ankle therefore does less work .
This splints the ankle. In doing so it has two actions. Firstly it reduces the forces through the ankle by acting like an "exoskeleton", allowing weight to bypass the inside of the joint. Secondly it physically restricts the movements which the ankle is able to make, therefore reducing the forces passing through the symptomatic joint.
Generally in lower demand patients, often those in their seventh or eighth decades.
As long as symptoms are limited to weight bearing activity and not present when resting or during sleep, an orthotic may well reduce pain significantly.
Once pain is not related to weight bearing an orthotic which reduces the weight bearing forces through the ankle makes less difference.