Patients with joint contractures (joints that are limited in their range of motion and cannot fully straighten or bend) and pterygium (webbing) are also treated using the gradual stretching technology. Some joint contractures are treated by surgically lengthening muscles and tendons, whereas more severe joint contractures require the gradual stretching provided by external fixation. After the contracture is corrected, the external fixator remains in place, often for the same period of time it took to achieve the correction gradually. This allows the soft tissues that have been stretched to relax and helps prevent recurrence.