X-ray of the right breast (mammogram) of 61 year old female patient showing capsular contracture of a breast implant. The patient had the breast augmentation at age 35. Capsular contracture is an abnormal immune response to foreign materials such as breast implants, heart pacemakers and prosthetic joints. Normally, a capsule of collagen fibre forms around the foreign object, creating a compartment that separates it from the rest of the body. In capsular contracture, the collagen tightens, squeezing the object. This causes pain, restricted movement and a distorted shape. The exact cause of contracture is not known.