One of the most common cause of anterior knee pain is Patellofemoral pain syndrome.
People (especially runners) typically report pain around or behind the knee cap during activities such as running, squatting, stair climbing.
It is perceived that pain around the knee cap (Patellofemoral joint) arises due to maltracking of the patella.
Exercises can be used to target the hip, knee and ankle to help improve patella arthrokinematics to facilitate smoother tracking of the patella.
As usual, here are some exercise that may help reduce anterior knee pain.