Kneecap replacement (patellofemoral arthroplasty)
It's possible to replace just the under-surface of the kneecap and its groove (the trochlea) if these are the only parts affected by arthritis. This is also called a patellofemoral replacement or patellofemoral joint arthroplasty.
The operation has a higher rate of failure than total knee replacement – which may be caused by the arthritis progressing to other parts of your knee. Some surgeons advise a total knee replacement as the results are more predictable. Others feel that it’s better to preserve the rest of the knee joint if it isn’t affected by arthritis.
The operation is only suitable for about 1 in 40 people with osteoarthritis. However, the outcome of kneecap replacement can be good if the arthritis doesn’t progress and it’s a less major operation offering speedier recovery times. More research is needed to understand which people are likely to do well with this operation.