What kind of knee injury is this?

Patient: What could this injury be? I was doing squats and felt a minor pain in my left knee cap. After a few minutes the pain went away but the next day when i woke up my knee was sore and stiff. my knee was never swollen, bruised, no cracking, popping. its been 6 weeks now since i hurt it and its only about 50 percent healed.

Doctor: Knee pain is the most common presentation of patellofemoral syndrome. The pain typically is located behind the kneecap a nd often shows during activities that require knee flexion and forceful contraction of the quadriceps (e.i. during squats, ascending/descending stairs or pendants). Pain may be worsen by sitting with the knee flexed for a long period of time, such as while watching a movie, hence leading to the terms “theatre sign” and “movie-goer’s knee.” The causes are diverse: Overuse (repetitive use or activity), overloading, and misuse of the patellofemoral joint. The suggested strategy for conservative treatment should be as follows:  try exercises to strenghten Quads previous adequate stretching (weights or byke), pain control with ice packs after exercises, anti-inflammatory meds (i.e.: “Aleve”, “Advil”), identify and avoid those activities that can aggravate the pain. You could use during the acute pain episodes a knee sleeve with no pressure over the patella. Also, and very important, is the need for extended adherence to the exercise regimen, meaning keep a consistent daily routine of walking, or bicycle or gym (weights and stretching). Allow time for these conservative measures (i.e.: exercise program) to have an effect, usually 4-6 weeks is adequate for some resolution of symptoms.