Immobilization is the process of holding a bone or joint in place with a cast, brace or splint. This prevents the injured area from moving as it heals. Immobilization restricts motion in the injured area and allows it to heal properly. It can help to reduce pain, muscle spasms and swelling. The immobilizer allows for the proper alignment in the healing process. When a limb, like an arm or a leg has been injured, one of the main reasons to immobilize it is to prevent it from being injured again.