Review Question - QID 212526

A 17-year-old girl comes to the primary care clinic with her father complaining of right knee pain. She reports that the pain started about a month ago, and since then it has gotten progressively worse. The knee pain is not constant but becomes most noticeable when going up or down the stairs. She also endorses that her knee becomes uncomfortable towards the end of class. Her father is worried because the pain is affecting her ability to play basketball, and she has college scouts coming to watch her play. The patient has no chronic medical conditions. She had a tonsillectomy as a child. She takes a multivitamin and uses ibuprofen as needed for the pain. On physical examination, there is tenderness at the inferior pole of the patella, without swelling or overlying skin changes. Which of the following is the most likely diagnosis?