Pain at the inner or medial part of the knee is a common complaint in active adults including hikers and runners.
People often complain of tenderness to the touch and also pain and limitations going up and especially down hills or stairs.
When people go looking for answers to this problem, they often end up getting an explanation of what hurts. Medial ligament strain...bursitis (swollen fluid filled sac)...tendonitis (swelling of a tendon)....etc.
In my experience this naming of what hurts in a fancy way as I like to think of it, is not all that helpful in getting to the root of what is causing the pain.
Write something about yourself. No need to be fancy, just an overview.