Wiktionary
n. Any device inserted into a shoe to lift the heel of the wearer, for the purpose of making the wearer appear taller, or correcting a limb length discrepancy.
Wikipedia
A removable shoe insert, otherwise known as a foot orthosis, accomplishes many number of purposes, including daily wear comfort, foot and joint pain relief from arthritis, overuse, injuries, and other causes such as orthopedic correction, smell reduction and athletic performance.
Medical use of foot orthoses has been criticized as lacking evidence of benefit, and practice is very inconsistent: reputed podiatrists prescribe completely different orthoses for a single patient. Further, effect of a given design of orthosis varies significantly by patient, and standard practice to personalize prescription is not available. However, evidence is mixed: patients often report at least short-term improvements in comfort, and other studies have found effectiveness.
Usage examples of "shoe insert".
Of firm but pliable rubber, custom-formed to his disfigured foot, a shoe insert filled the void left by his missing toe.