Orthotics include a broad range of physical aids used primarily to correct structural problems in the feet, knees, lower back, neck, and wrists. An orthotic may be any orthopedic device that is external to the body. Orthotics is also the name given to the medical field that provides specialized consultation and advice concerning corrective devices. Orthotics are distinguished from prosthetic devices, which are artificial or mechanical devices that replace an absent limb.

An orthotic may have one or more purposes, including to provide support to a limb or joint; to protect and prevent a part of the body from exposure to a particular range of motion; to assist in a particular function or movement; and to correct a specific structural weakness or imbalance, particularly through the realignment of the joint or structure.

The most common orthotic devices are foot orthotics, which are designed to correct the irregularities in the runner's gait that lead to both uneven foot strikes on the ground and consequent injuries; neck braces, which are primarily to restrict neck movement when the person has sustained a neck muscle sprain or similar injury; a back support, often referred to as a truss or girdle, designed to provide additional support to the lumbar vertebrae and muscle structures; knee braces of various kinds, all of which are structured to provide support to the joint where it has sustained a structural injury such as ligament damage, as well as to restrict it from being bent or twisted; and wrist supports, which are designed to maintain the strength of the wrist, in conjunction with the thumb joint.

For athletes, the most common reason for orthotic use is the desire to correct an inherent structural or alignment problem, most often in the manner in which the athlete runs. When the athlete has one leg longer than the other or the arch of one foot higher than the other, the running motion will naturally generate unequal forces from the moment the foot strikes the ground. This force radiates into the sole of the foot, particularly the plantar and heel, through the ankle joint, along the lower leg, into the knee, and is ultimately absorbed by the hip joint. Each of these points is vulnerable to the repetitive nature of the running motion, causing damage to its structure. An orthotic, typically a lightweight molded insert, will be custom designed for the runner to be worn on the inside of each shoe to create a more even footfall and correspondingly equitable distribution of the forces. These shoe insert orthotics have become quite popular and are not restricted to correction of alignment of the structures of distance runners. The efficiency and the ultimate performance of athletes in every running discipline will be influenced by structural misalignment, including track running and all field sports.

Brace orthotics perform a different role for the athlete. Neck and knee braces, the most common of these appliances, are intended primarily to restrict the ability of the subject joint to move in a fashion that might cause a re-injury. Neck braces, modified to fit even an American football player while wearing other protective equipment, are sometimes worn by players who have either sustained a minor neck muscle strain or who have a history of neck problems. The neck brace will assist in the prevention of the neck being extended. In a similar fashion, knee braces are almost always worn by athletes who have sustained a previous injury, often to the medial or anterior cruciate ligament (ACL), the connective tissues that essentially hold the femur (thigh bone) to the tibia and fibula (shin bones). When the athlete has had reconstructive ligament surgery, the brace serves to prevent the knee from being forced from one side to the other, which places undue stress on the repaired joint.

To provide the maximum degree of desired support, an orthotic brace must extend beyond the target joint. Knee braces that are the most supportive will extend from the calf muscles, with a hinge at the joint, to the quadriceps. Effective ankle braces will often be designed to extend from the top of the Achilles tendon, secured at a point near the forefoot.

The best orthotics are those custom-made for the individual. A foot orthotic will be constructed from a casting made of the foot of the athlete; the relevant medical specialist, often a podiatrist, will often utilize a video image of the gait to best determine how to customize the device to suit the particular needs of the athlete.

SEE ALSO Knee: Genetic and non-athletic conditions affecting performance; Musculoskeletal injuries; Running injuries; Running shoes;.