One of the things I have always checked, but have been finding more and more recently, is bilateral tender points on the inside knee. Find your Pes Anserine insertion. This is on the inside tibia. This is the common insertion for your Sartorious, Gracillis and Semitendinosis. Follow the muscles up about two inches and press in. If both sides are painful, it may be a clue that you have stressed adrenal glands.
How have you been sleeping? Has your sugar or caffeine intake been higher then normal? Have you had a craving for more high starch type carbohydrates. These questions will all be clues for potential adrenal fatigue or stress.
A few things to eliminate to help with an Adrenal Stressed Diagnosis. Make sure both arches are not collapsing, so both tibia's are not internally rotating. I usually check to make sure both Tibialis Posterior muscles aren't tight and painful as well. This will help eliminate a biomechanical cause.
What I have found as effective treatment is supplementing with Vitamin C, 3000mg for 10-14 days. If they are open to taking it, Rhodeola Rhosea as well. Eliminating the sugar for the same two week time period and trying for naps and earlier bed time if possible. Usually in two weeks time, the knee pain is gone.