I allow you the flexibility to bend down and move around. I am controlled primarily by your kidney energies. The kidney energies relate to fear and willpower.
I have alway been a strog metaphor for you in your life. I represent your willpower. When, as a child, you wanted to summon your willpower in defiance, you would lock your knees. You learned the metaphor of bending your knees in submission to your God, your leader or your victor. When you have issues around your willpower, they will reflect in disturbances in my function.
You use willpower to help overcome fear - the other energy of the kidneys. These two opposing forces within the kindeys represent the two opposing forces of the Fire and Water balance in the dualistic yang/yin function of the kidneys.
When you experience extreme fear, your knees will go weak. Fortunately, that doesnt happen too often in modern society. Something else happens though, that can be more destructive because of its insidious nature. In modern society, the biggest fear is the fear of coping. Fear of coping with money, work, relationships, health, etc. When you live with this kind of fear, I will become weakened and prone to injury. If it is prolonged over a long period of time and is coupled with weakened willpower to overcome the fear, then my brain will strengthen me by making me inflexible and rigid. You will call this arthritis.
The inner side of my is controlled by the spleen/pancreas. So if you hurt my medial ligaments, then you ar worrying about something that you are not coping with. (The spleen/pancreas controls worry.)
My outer side is controlled by the gall bladder so if you injure that part, you are fearful of making a decision about something.
The cruciate ligament deep inside my center relates to the deepest aspect of willpower - the will to survive. When I am injured, you are usually deeply questioning aspects of your life and existance. This does not mean you are suicidal, just that you are deeply questioning your life, its direction, and your will to flow through and do what needs to be done in your life.
The bladder controls the back of me. The bladder meridian profoundly influnces the central nervous system and activity. When that part of me is injured, it usually relates to your allowing your willpower to become over controlled by your nervous system. You become rigid, inflexible and fearful underneath. You 'stand up' for yourself in too reactive a way.
If your hamstrings and also involved, the colon (letting go) controls them. That means that you are fearful of letting go of the 'stance' you are taking- to your detriment. Usually, I start aching in the back when you are going through a period of your life when your belifes are being challenged and you are afraid to let them go.