There was an article not too long ago in the american journal of sports med. It was a prospective study where they looked at a bunch of asymptomatic athletic young people. They followed them for several years and then retested them on a number of measures. A certain percentage of these subjects developed anterior knee pain during the study. The major differences noted were that the subjects who developed anterior knee pain had tighter quads and gastrocnemius than those who didn't.
In other words, stretch your quads and gastrocs.
I've yet to treat anyone with anterior knee pain that didn't also have hip weakness on the same side. Glute max and glute medius activation/strengthening. Start with simple isolation exercises and progress to shallow single leg exercises with an opposite leg reach to front side and rear (activates hip muscles). 0-30 degress is usually not painful.
Rehab VMO if it has developed stretch weakness. The horizontal fibers of VMO will tend to be weaker if the hip is weak.
TFL can also be overactive especially if your psoas is weak. There is a slip of you ITB that attaches to the patella that can affect tracking. TFL attaches to ITB. If glutes are weak, hip will internally rotate when loaded and alter patellar tracking.
Test your psoas. Sit on a low bench with hips slightly lower than knees. Knees are bent greater than 90 degress. hands behind back. Maintain neutral spine (hands can monitor this). Raise one knee and then the other. Identify weakness by inability to raise knee significantly without altering back position.
If psoas is weak, iliacus becomes more dominant. Because it has no influence above the pelvis like the psoas, anterior tilt increases. Couple that with TFL overactivity. Anterior tilt promotes internal hip rotation and lateral patellar tracking.
If weak, strengthen psoas.
If you've ever sprained the ankle on the knee pain side, check your fibularis muscles (AKA peronei...name change recently in texts to avoid getting mixed up with peroneum) for tenderness and tightness. This will cause eversion at the ankle and internal rotation of the tibia and promote lateral tracking of patella.
Foam roller everything or get some serious soft-tissue work.
That should give you something to work on.
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