① Stabilize the joints. For example, the flail knee caused by poliomyelitis, the muscles that control the extension and flexion of the knee joint are paralyzed, the knee joint is soft and unstable, and it is overextended, which hinders standing. The knee joint can be controlled in a normal straight position with a brace.

② Protect the bone graft or fracture to replace the weight. For example, for ankle injuries, the brace can be used for protection before the fracture is completely healed.

③ Correct the deformity or prevent the deformity from getting worse. For example, patients with mild scoliosis below 40° can wear a brace vest to correct the scoliosis and prevent it from getting worse.

④ Replace the function. For example, when the hand muscles are paralyzed and weak and cannot pinch and grasp objects, the brace can be used to support the wrist joint in the functional position (dorsiflexion position), and an electrical stimulus can be installed on the forearm of the brace to stimulate the contraction of the flexor muscles to restore the pinching function.

⑤ Assist in hand function exercises. For example, a brace that supports the wrist joint in the dorsiflexion position to practice the flexion of the metacarpophalangeal joint and interphalangeal joint, and an elastic brace that keeps the fingers flexed to practice finger straightening.

⑥ Make up the length. For example, when a patient with shortened lower limbs stands and walks, the pelvis will inevitably tilt, and the tilt of the pelvis causes compensatory bending of the lumbar spine, which may cause low back pain over time. In order to make up for the length of the short limb, the sole of the shoe can be raised, which is called a height-compensating shoe.

⑦ Temporary external fixation. For example, a neck collar is worn after cervical fusion surgery, and a waist collar or vest is worn after lumbar fusion surgery.

With the popularization of rehabilitation medicine, low-temperature and high-temperature thermoplastic sheets and resin materials are constantly introduced, and various types of braces based on biomechanical design theory are constantly being developed. With their advantages of simple operation and strong plasticity, they can replace plaster and are widely used in clinical practice. Braces can be divided into eight categories according to different parts of use: spine, shoulder, elbow, wrist, hip, knee, and ankle. Among them, knee, shoulder, elbow, and ankle braces are the most widely used.