Anterior knee pain can be from a number of factors but one of the most often seen issues is Chrondomalacia Patella (CMP) or poor tracking of the patella.
With weak VMO also look for glute misfiring also as often the two go hand in hand causing that medial bow in the upper leg.
Terminal knee extensions and Petersen stepups are very good for VMO firing, but also 1&1/4 squats (at the bottom of the squat) as the VMO fires coming out of full flexion as far as I can remember also.
I do remember one case of what I thought was CMP and I treated it as such, but this only resulted in more pain so I treated it as hypertonic quadriceps in general rather than misfiring VMO and this relieved the pain immediately – just pointing out that the misfiring can also be simply a case of hypertonicity rather than weakness of VMO.