Patellofemoral arthritis due to localize nodular synovitis (LNS).

We present the case of a 38-year-old female patient who had suffered from a progressively increasing anterior pain in her right knee for almost 10 years. She decided to seek medical advice when the pain became intolerable, not permitting her to perform normal everyday activities. The clinical examination showed evidence of patellofemoral arthritis, but the MRI that followed, apart from confirming the original diagnosis as an "Outerbridge" grade III osteoarthritic lesion, revealed an unidentifiable tumor located in the lateral part of the right patellofemoral joint, that appeared to be like a type of "reactive synovitis". The articular degeneration was treated with arthroscopic saving, followed by complete excision of the tumor and anteromedial tibial tubercle transfer under direct vision. The excised tumor was histologically categorized as a "localized type of nodular synovitis" otherwise known as "giant cell" tumor of synovial origin. The patient has fully recoreved from surgery and 3 years post-operatively she has fully returned to everyday normal activities noting only occasional slight discomfort.