A dear friend of mine suffers from knee pain without there being any injury. The cause is actually from the bad alignment, when the pelvic- and core area don’t support the hip joint well and the thighs rotate slightly internally and the knees come closer together. The misalignment usually comes with feet that pronate (the arch of the foot falls down) and this only reinforces the malalignment of the legs.
Training the hips and the core will help stabilise and support the joints. So I put together three videos showing some of the exercises I use to help my patient train their way out of this kind of knee pain.
Just remember to be aware of your feet, and actively put the weight on both the base of the big toe and the base of the little toe to suport the arches of the feet.