Alignment and control
This is about looking upstream and downstream, the patellofemoral joint does not like a rotary component which can be caused by poor lumbopelvic control (what the core/hip is doing) upstream or poor foot biomechanics (what the foot is up to) downstream.
Technique
How do the movements look unweighted, weighted and when fatigued?
Load management
There is usually a load related component so it is always worth looking at how much you are doing currently vs what you were doing previously and furthermore how to plan the load to ensure it improves. Gradual loading is the best loading (3).
Strength
How strong are the glutes and quad muscles as these 2 groups of muscles are shown to be very important when it comes to patellofemoral pain (1-3). Additionally, how strong are the calves, groin, core and hamstrings? If everything is stronger than even better! There is a significant reduction in injury risk with increased strength (4-5).
Range of motion
Are there restrictions elsewhere in the biomechanical chain causing the knees to compensate?
Is there a previous ROM limitation at the ankle due to a previous injury causing the knee to compensate? Is there limitations/tightness in the hamstring or calf? Is there significantly limited thoracic extension causing you to fall forward placing excess strain on the knees during squatting or overhead movements? Is the foot rolling outwards to make up for restricted ankle ROM (1-3)?
How best to approach it?
Unfortunately, patellofemoral pain is often a very niggly condition and a large number of people experience ongoing issues even with some form of treatment (6). As patellofemoral pain is such a multi-faceted condition it requires a very thorough approach to specifically address all the potential contributing components. It will take time but it is important to be consistent, thorough and methodical in the approach to get best results.
General areas to address:
Alignment and control
Lumbopelvic control
Foot mechanics
Technique
Load management
Strength
Range of motion