Amitriptyline is a tricyclic antidepressant which is used to relieve the chronic (long-term) pain of arthritis and related conditions.It relaxes muscles and improves sleep that’s being disturbed by pain, and it may also help with anxiety or depression resulting from the pain.mitriptyline used to treat chronic (long-term) pain caused by arthritis, neck and spine problems, fibromyalgia, chronic headaches and peripheral neuropathy (damage to nerve endings in the upper and lower limbs).