Failed Total Knee Replacement
All knee replacements contain a polythene bearing, and over a period of many years wear of this bearing results in the accumulation of tiny fragments of polythene debris within the knee joint. This causes a chronic inflammation, softening and damaging the supporting bone and eventually resulting in loosening of the replacement, which is the commonest mode of failure.
Occasionally the polythene bearing collapses completely allowing the metal running surfaces to wear directly against each other releasing metallic swarf, and very occasionally the replacement itself or the supporting bone cracks or fractures. Other causes of failure include deep infection or instability of either the knee cap joint or the knee joint itself.