Orthotics is a specialty within the medical field concerned with the design, manufacture and application of orthoses. An orthosis (plural: orthoses) is an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. An orthotist is the primary medical clinician responsible for the prescription, manufacture and management of orthoses. Orthotics combines knowledge of anatomy and physiology, pathophysiology, biomechanics and engineering. Patients who benefit from an orthosis may have a condition such as spina bifida or cerebral palsy, or have experienced a spinal cord injury or stroke. Equally, orthoses are sometimes used prophylactically or to optimize performance in sport.