A prescription orthotic is used to treat all sorts of foot, leg and even lower back problems.  Prescription orthotics are further divided into two types. One is an accommodative orthotic. This device as the name implies accommodates a problem. For example, if you suffer from very arthritic feet an accommodative orthotic may be built that would better support your feet in an effort to reduce the stress being placed on the arthritic joints and not force the joints to have to go through their full range of motion which is what usually causes pain, since the primary sign of arthritis is the limitation of motion in the affected joint.

The other type of prescription orthotic is known as a functional orthotic. This is a type of orthotic that is built in an effort to change the way the foot functions in the gait cycle, to make up for the deficiencies in an individual's anatomical make-up. This type of orthotic attempts to change the biomechanics of the foot, which in turn may have a positive impact in the skeletal system all the way up to the lower back.

In order to make a prescription orthotic either a plaster of paris cast is taken of both feet in their neutral position, the ideal relationship of the feet to the legs. These casts are sent to a professional lab where an orthotic is fabricated based on the recommendations of the prescribing doctor.  

In many instances, instead of taking a plaster of paris cast, we will "scan" the feet and are able to send the impressions immediately to the lab. This is a newer technology and I have been very happy with the results that I have seen in the finished product.

Prescription orthotics can be made out of a multitude of materials and may have various additions added to them based on the patient’s problem. For example, a patient with a supinated foot, generally exhibits poor shock absorption as his foot hits the ground. This inability of the foot to absorb shock allows the “shock wave” to travel up the leg where is can manifest itself as pain all the way to the lower back. In this case the prescription orthotic may be built out of materials that help absorb shock.

• metatarsalgia
• Heel spurs, plantar fasciitis
• Shin splints
• Ankle instability
• Arthritic conditions of the foot and ankle
• Sesamoiditis
• Diabetic foot protection and partial foot amputations
• Running injuries including runner’s knee
• Forefoot pain such as capsulitis, neuroma
• Treatment for mild bunions and hammertoes
• Pediatric problems such as in toeing and out toeing
• Juvenile bunions
• Apophysitis in children
• Adult biomechanical abnormalities
  

There are a number of issues here.

First, store bought supports are sold by shoe size, not foot structure. So if you are a size ten shoe and buy a size ten arch support you have to hope that your arch support happens to be the same as your foot structure. There are any number of foot structures in the human anatomy, but you may be the lucky individual whose foot structure matches the arch support.

In addition store bought arch supports do not address the weight of the patient. It would stand to reason that a person weighing 250 pounds would have different support needs than someone who weighs 150 pounds. Although I cannot state that I have seen every arch support sold in drug stores and supermarkets, I can say that I have never seen one that is much better than the arch supports that come in a good pair of sneakers. So an easy rule of thumb might be that if you are having pain in spite of wearing reasonably good sneakers with a built in arch then purchasing a store bought arch support is probably a waste of your time and money.

Next, you have to hope that the arch support is built out of the material best suited to help your foot problem. Many prescription orthotics have padding added and cutouts made in certain parts of the orthotic to accomodate various foot problems. Your problem is that store bought arch supports do not come with any additions for specific foot problems like the prescription orthotics do.

Lastly, most store bought arch supports are more about cushioning then actual support. Unfortunately, most lower extremity problems require support and not cushioning in an effort to relieve pain.