Swelling and puffiness can be caused by a knee replacement failure occurring years after the surgery, says the Hospital for Special Surgery. A knee replacement often fails due to the normal wear and tear put on the implant over the years.
A knee replacement can fail after years of use because of loosening, infection, instability, stiffness and infection of the implant, according to the Hospital for Special Surgery. Once this happens, the area starts to swell, accompanied with pain and stiffness. The implant loosens when surfaces rub against one another as the person moves and bends his knee. Over the course of time, the implant loosens, while parts of the bone are worn away. Sometimes the implant fractures, causing instability and swelling.
Sometimes a knee replacement swells and fails because of bacteria that find a hospitable breeding ground on the surface of the implant, states the Hospital for Special Surgery. The implant can even become stiff, causing not only stiffness and swelling, but a loss of movement in the joint itself. Occasionally, the implant doesn't fail as much as the tissue around it does. The soft tissue around the implant becomes weak and refuses to support the implant. This makes the implant unstable.