Here are the opertive approaches:
1. Arthroscopic debridement
2. Microfracture articular restoration
3. Lateral release
4. Soft-tissue realignment of the extensor mechanism
5. Osteotomies of the tibial tubercle
6. Mosiacplasty/autologous chondrocyte implantation
7. Lateral patella partial facetectomy
8. Patellectomy (removal of the kneecap)
9. Total knee replacement

And as this wasn't enough:
"While operative replacement of any portion of the knee joint is one of the last options,it is often the only good choice left when other treatments fail of result in increased pain. We have found a definite trend of more rapid recovery,better function, more predictable return to work,and decreased dependency on pain medication with this operation. Patients can become very depressed and socially drained by the stress of constant pain and ineffectual prior treatment. Patellofemoral replacement offers more predictable relief from these problems in our experience."
LINK