Physical therapy is an exercise treatment for patients who have been immobilized or impaired in their movement and flexibility. Patients are rehabilitated to use their own muscles to increase flexibility and range of motion as well as to advance to higher levels of muscular strength and endurance. To relieve pain and reduce swelling, physical therapy often includes the use of modalities, or passive physical therapy, such as electrical stimulation, hot packs, cold compresses, and ultrasound. Traction or deep-tissue massage may also be used to relieve pain. When necessary, therapists teach patients to use assistive and adaptive devices (such as crutches) as well as exercises to do at home to speed the recovery.