In practice, prefabricated insoles do have significant value in certain circumstances. For example, many people have a limb length discrepancy, either structural or functional. The body at times compensates for this inequality, but there are times when symptoms develop because of this difference. A leg length difference of ½ in. or greater often leads to low back pain, hip pain, and, many times, creates pronation of the longer leg creating foot and ankle issues such as posterior tibial tendonitis and plantar fasciitis. Adding a heel lift onto an over-the-counter shoe insert to compensate for the limb length discrepancy will certainly be helpful.

The athlete with an atrophic fat pad and complains of pain under the metatarsal heads and/or under the heel may benefit from a prefabricated insole with additional cushioning.⁵ Several years ago, it was believed that injection of collagen would benefit such a patient, using it to replace the natural fat cushion lost in the aging process. This procedure proved both costly and ineffectual as it was often displaced and/or lost after a few weeks of weight-bearing. One of the best methods of resolving this complaint is simply cushioning the foot with a full length, soft or semirigid, over-the-counter device. In addition, athletes who play on unyielding surfaces such as asphalt or concrete may also benefit from such cushioning, especially when they wear thin-soled athletic shoes.

Many forms of arthritis are also characterized by degenerative changes that lead to dorsal subluxation of the toes and plantar prominence of the metatarsal heads. Prefabricated insoles are often beneficial in treatment of these individuals. In addition, modifications can be placed on top of or underneath the insert (Fig. 9.2) to further disperse weight from one particular area.

Diabetic athletes may also benefit from a prefabricated insole. Foot problems commonly seen in diabetic patients include vascular impairment, neuropathy, atrophy of the soft tissues, and deformity. The importance of addressing insensitivity, paresthesias, decreased vibratory sense, and motor weakness cannot be stressed enough. Motor neuropathy is commonly believed to lead to weakness in the intrinsic muscles of the foot, upsetting the balance between flexors and extensors of the toes.⁶ Atrophy of the small muscles responsible for metatarsophalangeal plantar flexion is thought to lead to the development of hammer toes, claw toes, and prominent metatarsal heads. These deformities are common sites of abnormally high pressure, and repetitive pressure at these sites could result in the buildup of calluses and/or ulceration.

These patients will benefit from prefabricated insoles for the same reason as stated earlier. The insoles can also be easily modified with dispersion using a U-shaped pad or metatarsal pad (Fig. 9.3). These are very helpful in off-loading an area that may be predisposed to ulceration. Diabetic athletes need to be monitored closely and the off-loading material may need to be increased in thickness or placed in other positions if one sees that there is still pressure in a sensitive area.