Patellofemoral Problems...
When your knee just doesn't feel right especially when walking/running downhill, what is going on? Your knee cap, or patella, may not be tracking properly with the bones it contacts, the femur and the tibia.
One likely cause of this is weakness in the hip abductor muscles. (These are the muscles that bring your leg out to the side.) Here are some excellent exercises to help strengthen these muscles. Try this little routine every day for two weeks and see if it helps!
Let me know how it goes!
Fredericson M, Powers CM. Practical Management of Patellofemoral Pain. http://www.mpi.twodotdev.com/wp-content/themes/movement_pi/publications/Practical_management_of_patellofemoral_pain.pdf. Accessed Dec 12 2016.