Capsular contracture is a response of the immune system to foreign materials in the human body. Medically, it occurs mostly in context of the complications from breast implants and artificial joint prosthetics. Capsular contracture is a response of the immune system to foreign materials in the human body. Medically, it occurs mostly in context of the complications from breast implants and artificial joint prosthetics. The occurrence of capsular contraction follows the formation of capsules of tightly-woven collagen fibers, created by the immune response to the presence of foreign objects surgically installed to the human body, e.g. breast implants, artificial pacemakers, orthopedic prostheses; biological protection by isolation and toleration. Capsular contracture occurs when the collagen-fiber capsule shrinks, tightens and compresses the breast implant, much like the collapse of a bubble gum bubble. It is a medical complication that can be painful and discomforting, and might distort the aesthetics of the breast implant and the breast. Although the cause of capsular contracture is unknown, factors common to its incidence include bacterial contamination, rupture of the breast-implant shell, leakage of the silicone-gel filling, and hematoma.